yv_-ir_n_ 


REESE  LIBRARY 

OF    ! 

UNIVERSITY  OF  CALIFORNIA. 


No.  ^//  ^  9  fa  .    C7.7S5  No. 


SPECTRUM    ANALYSIS, 


BY 

JOHN    LANDAUER,    LL.D., 
»> 

Member  of  the  Imperial  German  Academy  of  Naturalists. 


AUTHORIZED   ENGLISH  EDITION 

BY 
J.    BISHOP    TINGLE,    PH.D.,    F.C.S., 

Instructor  of  Chemistry  in  the  Lewis  Institute, 
Chicago,  III. 


FIRST   EDITION1. 
FIRST    THOUSAND. 


NEW  YORK: 

JOHN   WILEY  &   SONS. 

LONDON:  CHAPMAN  &  HALL,  LIMITED. 

1898. 


Copyright,   1898, 

BY 
J.   BISHOP  TINGLE. 


ROBERT  DRUMMOND.    ELECTROTYPES   AND   PRINTER,   NEW   YORK. 


AUTHOR'S  PREFACE. 


THIS  work  originated  as  a  reprint  of  an  article  on  Spec- 
trum Analysis  recently  contributed  to  Fenling-Hell's  "  Neues 
Handworterbuch  der  Chemie  ";  it  was  published  as  a  sepa- 
rate book  at  the  request  of  a  number  of  competent  authorities, 
but  not  without  some  hesitation  on  the  part  of  the  author, 
because  in  treating  a  subject  in  an  encyclopedic  article  regard 
must  be  paid  to  the  whole  plan  and  scope  of  the  work,  whilst 
in  a  separate  book  the  author  is  quite  independent. 

The  favorable  reception  accorded  to  the  book  when 
published  gives  rise  to  the  hope  that  shortcomings  arising 
from  its  origin  are  to  some  extent  counterbalanced  by  a 
fulness  of  contents  brought  together  in  small  space,  by  the 
strictly  historical  treatment  of  the  subject  adopted  through- 
out the  book,  by  tolerably  full  bibliographical  references,  and 
by  the  care  which  has  been  bestowed  on  the  numerical  tables 
serving  for  reference.  In  order  to  secure  a  degree  of  uni- 
formity hitherto  wanting,  the  older  measurements  have  been 
recalculated  so  as  to  bring  them  into  accord  with  Rowland's 
system  of  wave-lengths. 

THE  AUTHOR. 

BRAUNSCHWEIG,  1898. 

iii 


ABBREVIATIONS. 


THE  following  abbreviations  have  been  used  in  the  biblio- 
graphical references: 

A.  B.  A.  =  Abhandlungen  der  Koniglichen  Akademie 
der  VVissenschaften  zu  Berlin. 

A.  c.  p.  =  Annales  de  chimie  et  de  physique. 

B.  A.  R.         =  British  Association  Reports. 

C.  N.  =  Chemical  News. 

C.  r.  =  Comptes  rend  us  hebdomadaires  des  Seances 

de  1' Academic  de  Sciences,  Paris. 

N.  =  Nature. 

N.  A.  S.  U  =  Nova  Acta  Regiae  Societatis  Scientiarum 
Upsaliensis. 

p.  A.  =  Poggendorff's  Annalen  der  Physik  und 

Chemie. 

P.  M.  =  Philosophical  Magazine. 

P.  M.  P.  S.  =  Proceedings  of  the  Manchester  Literary  and 
Philosophical  Society. 

P.  R.  S.  =  Proceedings  of  the  Royal  Society. 

P.  R.  S.  E.  —  Proceedings  of  the  Royal  Society,  Edin- 
burgh. 

P.  T.  =  Philosophical  Transactions. 

P.  T.  E.          =  Philosophical  Transactions,  Edinburgh. 

T.  R.  S.  E.  =  Transactions  of  the  Royal  Society,  Edin- 
burgh. 

W.  A.  =  Wiedemann's  Annalen  der  Physik  und 

Chemie. 


TRANSLATOR'S  PREFACE, 


THE  claim  of  spectrum  analysis  to  a  place  in  a  chemical 
curriculum  is  steadily  obtaining  increased  recognition,  and  its 
importance  is  generally  admitted  both  for  students  preparing 
for  teaching,  and  for  those  who  wish  to  engage  in  technologi- 
cal work.  The  subject  may  rightly  demand  a  wider  field  since 
its  pursuit  furnishes  so  many  opportunities  for  an  excellent 
training  in  accuracy  of  observation  and  manipulative  skill  that 
it  might,  with  great  advantage,  find  place  in  a  general  science 
course.  The  expense  is  by  no  means  prohibitive,  and  is 
almost  entirely  confined  to  the  first  cost  of  the  instruments, 
which,  with  proper  care,  last  for  years,  and  even  with  the 
cheaper  and  smaller  ones,  such  as  Browning's  "Students' 
Spectroscope,"  which  costs  about  $30,  much  interesting  work 
can  be  done  and  valuable  discipline  obtained. 

Of  the  works  on  spectrum  analysis  hitherto  published  in 
English,  none  are  suitable  as  text-books,  either  on  account  of 
their  size  and  consequent  cost,  or  from  the  manner  in  which 
the  subject  is  presented. 

It  is  hoped  that  this  little  book  may,  in  some  degree,  sup- 
ply this  lack. 

There  has  been  no  attempt  to  treat  the  subject  exhaus- 
tively, but  rather  to  indicate  the  more  salient  points  of  theory, 
etc.,  leaving  it  to  the  teacher  to  complete  and  expand  them 
at  his  own  discretion. 

No  doubt  it  would  be  well  if  all  students  were  compelled 
to  take  a  course  in  general  physics  before  attacking  chemistry, 


VI 11  TRANSLATOR'S  PREFACE. 

but  at  present  this  is  a  state  of  things  not  realized  in  practice ; 
to  those  who  have  followed  such  a  course  the  physical  section 
of  the  book  should  be  superfluous ;  but  it  may  serve  to  call 
the  attention  of  the  others  to  matters  on  which  they  should 
obtain  more  instruction.  The  tables  of  wave-lengths  will,  it 
is  hoped,  be  useful  in  the  practical  work  which  would  prob- 
ably constitute  the  greater  portion  of  the  course.  The  posi- 
tion of  the  more  prominent  lines  and  bands  can,  by  their 
help,  be  at  once  ascertained,  and  their  actual  occurrence  and 
identification  facilitated. 

LEWIS  INSTITUTE, 
CHICAGO,  ILL.,  Dec.  1897. 


CONTENTS. 


CHAPTER  I. 

PAGE 

INTRODUCTORY — HISTORICAL    .  t i 

Introductory,  i.  Historical,  2.  Bibliography  of  Works  on 
Spectrum  Analysis,  8. 

CHAPTER  II. 

PHYSICAL  PROPERTIES  OF  LIGHT n 

Wave-length,  n.  Reflection;  Refraction,  12.  Prisms,  13.  Dis- 
persion, 14.  Abnormal  Dispersion,  15.  Pure  Spectra;  Gratings, 
16.  Diffraction,  17.  Comparison  of  Diffraction  and  Refraction 
Spectra,  19. 

CHAPTER  III. 
SPECTROSCOPES  20 

Spectroscopes  with  Angular  Vision,  20.  Direct-vision  Spectro- 
scopes, 28.  Grating  Spectroscopes,  31. 

CHAPTER  IV. 

SPECTROSCOPIC  INSTRUMENTS  FOR  SPECIAL  PURPOSES     .        .        .        .35 

Spectrometer,  35.  Kriiss'  Universal  Spectroscope,  38.  Spec- 
trophotometer,  39.  Sorby's  Microspectroscope,  40.  Solar  and 
Stellar  Spectroscopes,  41.  Stellar  Spectrometers;  Spectrographs, 
43.  Rowland's  Concave  Grating  Spectrograph,  45. 

CHAPTER  V. 

SPECTROSCOPIC  ADJUNCTS          .        . 5* 

Flame  Spectra,  51.  Electric  Arc,  54.  Electric  Spark,  55.  Geiss- 
ler  or  Plucker's  (Vacuum)  Tubes,  58.  Observation  of  the  Invisible 
Regions  of  the  Spectrum;  Ultra-violet,  60.  Infra-red,  61.  Obser- 
vation of  Absorption  Spectra,  63.  Measuring  Appliances  and 
Scales,  65.  Drawings  of  Spectra,  68. 


X  CONTENTS. 

CHAPTER  VI. 

PAGE 

EMISSION-SPECTRA •        •        •  .69 

Line  Spectra,  71.  Influence  of  Temperature  and  Pressure,  72. 
Lockyer's  Long  and  Short  Lines,  73.  Influence  of  Magnetic 
Current,  75.  Absorption  Spectra;  Kirchhoffs  Law,  76.  Influence 
of  the  Temperature  and  the  Physical  State  of  Substances,  77. 
Influence  of  the  Solvent,  78.  Influence  of  the  Optical  Density; 
Fluorescence  and  Absorption,  79.  Relationship  between  the  Lines 
of  an  Element,  80.  Relationship  between  the  Spectra  of  Differ- 
ent Elements,  87. 

CHAPTER  VII. 

SPECTRA  OF  THE  ELEMENTS 92 

Unit  of  Measurement,  92.  Scale  of  Colors  ;  Delicacy  of  Spectrum 
Reactions,  95.  Spectra  of  the  Elements  (in  Alphabetical  Order), 
96. 

CHAPTER  VIII. 

ABSORPTION  SPECTRA 174 

Absorption  by  Gases  and  Liquids,  175.  Different  Salts  of  the 
same  Colored  Base  or  Acid,  177.  Relationship  between  Molec- 
ular Structure  and  Absorption  Spectrum,  178.  Absorption  in  the 
Visible  Portion  of  the  Spectrum,  179.  Absorption  in  the  Ultra- 
violet, 182.  Absorption  in  the  Infra-red,  184. 

CHAPTER  IX. 
THE  SOLAR  SPECTRUM       ..........   186 

The  Fraunhofer  Lines,  186.  The  Chemical  Composition  of  the 
Sun,  190.  Rowland's  Table  of  Wave-lengths  of  the  Fraunhofer 
Lines,  191.  Telluric  Lines  of  the  Solar  Spectrum,  201.  Limits  of 
the  Investigation,  202.  Physical  Condition  of  the  Sun,  203.  Solar 
Nucleus  ;  Photosphere  ;  Sun-Spots.  204.  Solar  Faculae  ;  Reversing 
Layer  ;  Chromosphere  and  Prominences,  205.  Corona,  207. 

CHAPTER  X. 

OTHER  CELESTIAL  BODIES .        .        .208 

Fixed  Stars,  208.  Planets  and  Moon,  209.  Comets;  Meteor- 
ites and  Shooting  Stars  ;  Nebulae,  210.  Aurora  Borealis;  Zodiacal 
Light;  Lightning,  211.  Displacement  of  the  Lines,  212. 


SPECTRUM   ANALYSIS, 


CHAPTER    I. 
INTRODUCTORY.     HISTORICAL. 

SPECTRUM  ANALYSIS  is  a  chemico-analytical  method  by 
means  of  which  it  is  possible  to  determine  the  constituents  of 
a  substance,  by  observing  the  refraction  (dispersion),  or  the 
diffraction  of  light-rays.  Its  further  development  offers  a 
means  of  investigating  the  molecular  structure  of  matter. 
The  image  which  is  produced  when  light-rays  are  refracted  is 
termed  a  spectrum.  White-hot  solid  bodies  emit  rays  of  all 
refrangibility,  and  give  a  continuous  spectrum;  glowing  gases 
or  vapors  emit  rays  of  definite  refrangibility,  and  therefore 
yield  a  discontinuous  spectrum  consisting  of  bright  lines  which 
are  characteristic  of  each  substance,  and  which  consequently 
serve  for  its  identification  whether  it  occurs  alone,  or  together 
with  other  bodies.  When  the  rays  from  a  white-hot  solid 
pass  through  a  colored  medium  some  of  them  are  retained 
giving  an  absorption  spectrum,  which  varies  with  the  chemical 
composition  of  the  medium. 

Spectra-reactions  are  characterized  by  an  extreme  delicacy 
far  exceeding  that  of  chemical  tests,  and  therefore  their 
employment  has  led  to  the  discovery  of  a  number  of  new 
elements  which  occur  only  in  small  quantity.  Since  the 
distance  of  the  source  of  light  has  little  effect  on  a  spectrum, 
the  method  can  be  employed  for  the  investigation  of  celestial 


2  SPECTR UM  ANAL  YSIS. 

bodies:  it  has  extended  our  knowledge  of  .their  nature  to  an 
extent  which  was  previously  entirely  unattainable. 

Historical.1 — Spectrum  Analysis  was  founded  by  Kirch- 
hoff  and  Bunsen  in  1859,  and  subsequently  developed. 
Other  observers  had  previously  noticed  spectrum  lines,  and 
had  suggested  the  application  of  spectroscopic  observations 
to  chemical  analysis,  but  their  efforts  were  fruitless,  as  at 
that  time  it  was  not  certain  whether  the  bright  lines  of  a 
glowing  gas  were  solely  dependent  on  its  chemical  composi- 
tion. The  sodium  reaction  was  particularly  misleading  as  it 
was  often  observed  when  the  presence  of  this  metal  was  not 
suspected,  and  was  therefore  variously  ascribed  to  sodium,  to 
sulphur,  or  to  water.  The  yellow  sodium  flame  was  first 
noticed  by  Thomas  Melville2  in  1752,  but  he  was  unable  to 
determine  its  origin.  John  HerscheP  in  1822  investigated 
the  spectra  of  many  colored  flames,  particularly  those  given 
by  strontium,  copper,  and  boric  acid,  and  in  1827  showed 
that  by  this  means  the  substances  giving  the  colors  could  be 
recognized  even  when  present  only  in  extremely  small  quan- 
tity. Fox  Talbot 4  in  1826  expressed  himself  still  more 
definitely,  stating  that  if  his  theory  that  certain  bodies  gave 
characteristic  lines  should  prove  to  be  correct,  then  a  glance 
at  the  prismatic  spectrum  of  a  flame  would  suffice  to. identify 
substances  which  would  otherwise  require  a  tedious  chemical 
analysis  for  their  detection.  In  1834  he  correctly  described 
the  lithium  and  strontium  spectra,  and  again  pointed  out  that 


1  Kopp,  Entwickelung  der  Chemie  in  der  neuren  Zeit  (Miinchen,  1873), 
pp.  215,  642.     Kirchhoff,  Zur  Geschichte  der  Spectralanalyse.     P.  A.  118, 
94,  102.     Brewster,  C.  r.  62,  17.      Kahlbaum,   Aus  der  Vorgeschichte  der 
Spectralanalyse    (Basel,   1888).      Rosenberger,    Geschichte    der    Physik,    3 
(Braunschweig,   1890).     Stokes,  N.   13,  188.     P.   M.  [4]  25,  250.     Talbot, 
P.  R.  S.  E.  7,  461. 

2  Edinb.  Phys.  and  Lit.  Essays,  2,  12. 

8  T.  R.  S.  E.  (1823)  9.     P.  A.  (1829)  16.      On  the  theory  of  light  (Lon- 
don, 1828) 

4  Brewster's  Journ.  of  Sci.  5.     P.  M.  (1833)  [3]  3,  35;  (1836),  9,  3. 


IN  TROD  UCTOR  Y.  HIS  TO  RICA  L.  5 

such  optical  methods  permitted  of  the  identification  of  these 
elements  with  a  minimum  quantity  of  substance,  and  with  an 
exactitude  equalling,  if  not  excelling,  that  attained  by  any 
other  process.  Doubt  was,  however,  cast  on  this  conclusion 
by  contradictory  statements  in  the  same  communications,  and 
the  method  of  analysis  was  rendered  fundamentally  dubious, 
because,  in  opposition  to  Herschel,  Talbot  maintained  that 
the  reactions  could  be  produced  by  the  simple  presence  of  the 
substance  in  the  flame,  its  volatilization  not  being  necessary. 
W.  A.  Miller1  published  in  1845  an  investigation  on  trie 
spectra  of  the  alkali  metals;  diagrams  were  given,  but  the 
results  did  not  constitute  any  great  advance,  as  he  had 
employed  a  luminous  flame,  and  was  therefore  unable  to 
determine  what  was  characteristic  of  any  particular  metal. 
In  1856  Swan3  definitely  proved  that  the  yellow  line  which 
is  almost  always  present  is  peculiar  to  sodium  compounds, 
and  that  the  frequency  of  its  occurrence  is  due  to  the  almost 
universal  distribution  of  sodium  salts.  In  his  work  on  the 
prismatic  spectra  of  the  hydrocarbons  Swan  showed  that  the 
lines  observed  are  constant  in  position;  he  thus  made  a  valu- 
able contribution  towards  the  solution  of  the  question  as  to 
whether  the  bright;  lines  of  a  glowing  gas  are  exclusively 
dependent  on  its  chemical  composition.  The  de6nite  and 
general  answer  to  this  problem  was,  however,  not  given  by 
Swan,  but  by  Kirchhoff  and  Bunsen. 

The  spectra  of  the  electric  spark  had  been  under  obser- 
vation simultaneously  with  those  of  flames;  Wollaston  3 
detected  a  large  number  of  bright  lines,  but  without  offering 
any  clue  to  their  origin.  He  was  also  the  first  to  describe 
the  dark  lines  in  the  solar  spectrum,  and  he  improved  the 
apparatus  employed  by  substituting  a  narrow  slit  for  the  cir- 
cular opening  which  Newton  had  used  to  admit  the  light. 

1  B.  A.  R.  1845.  P.  M.  [3]  27,  Ci. 
2T.  R.  S.  E.  3,  376;  (1857)21,353. 
3  P.  T.  1802  p.  365. 


4  SPECTRUM  ANALYSIS. 

Fraunhofer1  was  scarcely  more  successful  than  Wollaston  so 
far  as  the  origin  of  the  bright  lines  was  concerned;  his  fame 
rests  on  the  discovery  of  the  diffraction  grating,  the  measure- 
ment of  wave-lengths  which  its  use  permitted,  and  on  the 
observation  of  the  dark  lines  in  the  solar  spectrum  which  bear 
his  name.  He  drew  350  of  these,  and  finding  that  they 
varied  from  those  observed  in  stellar  spectra,  he  concluded 
that  they  originate  in  the  sun  and  stars,  and  are  not  due  to 
the  earth's  atmosphere.  Wheatstone3  in  1835  found  that 
with  the  use  of  different  metallic  electrodes  the  spectra  vary, 
but  they  remain  constant  no  matter  whether  the  discharge 
takes  place  in  air,  hydrogen,  or  in  a  vacuum;  he  therefore 
concluded  that  the  metal  is  volatilized,  but  not  burnt,  by  the 
passage  of  the  spark.  He  published  drawings  of  the  spectra 
of  sodium,  mercury,  zinc,  cadmium,  bismuth,  tin,  and  lead, 
and  recommended  the  method  for  analytical  purposes. 

The  spectra  of  various  metals  volatilized  in  air  were 
studied,  although  less  thoroughly,  by  Foucault 3  in  1849;  ne 
also  observed  the  dark  /Mine,  since  known  as  the  reversed 
sodium  line,  but  failed  to  draw  the  important  conclusion  from 
this  which  Kirchhoff  subsequently  made.  Masson,4  who 
improved  the  method  of  working,  using  condensers  charged 
by  induction-currents,  investigated  the  spark-spectra  of  iron, 
tin,  antimony,  bismuth,  copper,  lead,  cadmium,  and  carbon; 
in  all  these  cases  he  noticed  that  the  lines  due  to  moist  air 
were  present,  although  he  was  ignorant  of  their  origin.  This 
was  indicated  by  Angstrom's  &  important  work  published  in 
-1853.  He  showed  that  the  lines  which  occur  in  the  space 
between  the  electrodes  are  due  to  air  or  to  any  other  gas 

1  Denkschriften  der  Miinchener  Akad.,   1814,   1815;  Gilbert's  Ann.  74, 
337- 

2  B.  A.  R.  1835.     C.  N.  3,  198.     P.  M.  [3]  7. 

3  Institut.  1849,  p.  44. 

*  A.  c.  p.  (1851)  [3]  31,  295. 

b  K.  Vetenskaps  Akad.   Handl.  (Stockholm,  1853),  P-  335-     P.  A.  (1855) 
94,  141. 


INTRODUCTORY.     HISTORICAL.  5 

which  may  be  present,  whilst  those  close  to  the  electrodes  are 
given  by  the  metals.  Angstrom  also  drew  and  described  the 
spectra  of  a  large  number  of  metals  and  non-metals,  and 
almost  discovered  the  relationship  between  the  emission  and 
absorption  of  light,  since  he  stated,  in  accordance  with  a  sug- 
gestion of  Euler,  that  at  a  common  temperature  bodies  absorb 
the  same  vibrations  which  they  are  capable  of  producing. 
In  1858  Plucker1  commenced  his  investigations  of  the  spectra 
produced  by  the  passage  of  an  electric  current  through  highly 
rarefied  gases.  He  found  that  the  elementary  gases,  or 
the  constituents  liberated  from  compound  gases,  are  char- 
acterized by  bright  lines.  Similar  work  was  pursued  by 
van  der  Willigen,2  who  in  1859  also  showed  that  platinum 
electrodes  moistened  with  a  salt  solution  give  the  spectrum 
of  the  salt,  and  that  it  is  therefore  unnecessary  to  use  the 
metal  itself  in  order  to  obtain  its  spectrum.  In  the  same  year 
Kirchhoff  and  Bunsen 3  published  their  work  "  Chemische 
Analyse  durch  Spectralbeobachtungen" ;  their  results  were 
obtained  to  some  extent  independently  of  previous  investiga- 
tors who,  whilst  frequently  on  the  right  path,  had  failed  to 
reach  the  goal.  They  reduced  spectral  phenomena  to  a 
chemical-analytical  method,  and  definitely  proved  that  the 
bright  lines  produced  by  a  glowing  gas  are  dependent  only 
on  its  chemical  composition.  This  law  still  forms  the  basis 
of  spectrum  analysis,  but  their  second  proposition  has  been 
subsequently  considerably  modified;  it  states  that  the  manner 
in  which  the  constituents  of  a  substance  are  combined  is  with- 
out influence  on  their  spectra,  and  that  these  are  also  almost 
entirely  unaffected  by  the  temperature  and  pressure  of  the 
vapor.  After  Roscoe  and  Clifton  4  had  called  attention  to  the 
difference  between  the  spectrum  of  an  element  and  those  of 
its  compounds,  A.  Mitscherlich  *  showed,  in  1863,  that  every 

1  P.  A.  103,  88;  104,  113,  622;  105,  67;  107,  77,  415. 

'l  P.  A.  106,  610;  (1859)  107,  473.  3  P    A.  110,  167. 

4  P.  M.  P.  S.    1862.  5  P.  A.  (1863)  121,  3. 


»"r  ^T  TTT-  T-I  T-»  r»i  T  m-«7- 


6  SPECTRUM  ANALYSIS. 

compound  has  its  own  peculiar  spectrum,  and  that  the  exhi- 
bition of  identical  spectra  by  the  various  salts  of  an  element 
is  caused  by  these  undergoing  dissociation.  In  their  first 
communication  Kirchhoff  and  Bunsen  described  the  spectra 
of  the  metals  of  the  alkalis  and  alkaline  earths,  and  showed 
the  great  delicacy  of  the  method,  which  permits  of  the  recog- 
nition of  substances  when  present  in  quantity  far  too  small 
for  detection  by  the  ordinary  processes;  they  also  pointed  out 
the  great  extension  which  it  gives  to  our  knowledge  of  the 
distribution  of  the  elements,  and  indicated  that  it  would 
probably  lead  to  the  recognition  of  new  ones.  The  correct- 
ness of  this  view  has  been  proved  by  the  discovery  of  caesium, 
rubidium,  thallium,  indium,  gallium,  and  many  metals  of  the 
rare  earths,  all  by  means  of  spectrum  analysis. 

The  development  of  spectrum  analysis  received  a  special 
impulse  from  its  application  to  astronomy.  Kirchhoff '  proved 
mathematically  that  for  every  ray  of  light  the  relationship 
between  the  emissive  and  absorptive  powers  of  all  bodies  is. 
alike  at  uniform  temperatures;  this  explained  the  origin  of  the 
Fraunhofer  lines,  and  led  to  the  investigation  of  the  chemical 
composition  of  the  sun  and  its  atmosphere.  The  discovery 
of  this  law  of  exchanges  induced  Kirchhoff  to  prepare  more 
exact  drawings  of  the  solar  spectrum,  and  to  accurately  com- 
pare the  positions  of  the  Fraunhofer  lines  with  those  in  the 
spectra  of  many  terrestrial  substances.  He  employed  for  this 
purpose  an  arbitrary  scale,  as  did  also  Huggins,2  who  extended 
these  observations.  To  Angstrom  3  belongs  the  credit  of  sub- 
stituting the  wave-length  for  the  scale  as  a  means  of  determin- 
ing the  position  of  the  lines,  and  his  measurements,  and  atlas 
of  the  solar  lines,  remained  for  twenty  years  the  foundation 
of  all  spectroscopic  investigations.  Angstrom's  work  was 

1  Monatsber.  Berl.  Akad.,  Oct.  27,  1859. 

2  P.  T.  (1864)  154. 

3  Recherches  sur  le  spectre  normal  du  soleil  avec  atlas  de  6  planches, 
Upsala,  1868. 


IN  TROD  UCTOR  F.     HIS  TO  RICA  L.  7 

confined  to  the  visible  portion  of  the  spectrum;  it  was  com- 
pleted by  Cornu's  *  researches  on  the  ultra-violet,  and  by 
Langley's2  and  Abney's3  on  the  infra-red.  After  Angstrom's 
death,  Thalen  4  showed  that  the  metre  he  had  employed  was 
incorrect,  and  that  consequently  his  wave-length  determina- 
tions were  too  small.  This  was  confirmed  by  Miiller  and 
Kempf 5  in  1886;  their  measurements  of  300  solar  lines  were 
carried  out  with  great  care,  and  became  the  basis  of  the 
Potsdam  system.  All  these  determinations  were,  however, 
exceeded  in  accuracy  by  Rowland's8  Atlas  of  the  solar  spec- 
trum, and  his  reproductions  of  normal  lines,  published  in  1888 
and  1893  respectively.  His  discovery  of  the  concave  grating 
in  1891,  and  his  "  coincidence  "  method  of  determining  the 
relative  position  of  lines,  has  greatly  aided  spectroscopic  work, 
since  it  admits  of  the  production  of  photographs  without  the 
use  of  a  lens,  thus  insuring  a  high  degree  of  comparative 
accuracy. 

For  a  considerable  time  the  measurement  of  the  spectra 
of  terrestrial  substances  did  not  keep  pace  with  that  of  the 
solar  spectrum;  Kirchhoff's  and  Huggins'  determinations  were 
duly  superseded  by  the  more  accurate  ones  of  Thalen,7  but 
these  were  confined  to  the  visible  spectrum.  Apart  from 
W.  A.  Miller's8  incomplete  work  on  the  ultra-violet  in  1862, 
Lockyer 9  in  1881  was  the  first  to  accurately  investigate  the 

1  Spectre  normal  du  soleil.     Partie  ultraviolette  (Paris,  1881),  p.  22. 

2  R  M.  [5]  21,  394;  22,  149;  26,  505. 

3  P.  T.  1880,  p.  653.     W.  A.  Beibl.  4,  375;  5,  507.     C.  r.  90,  182. 

4  Spectre  du   fer.  Acta  R.  Soc.  Sclent.  Upsala,  (1884)  [3],  p.  49.     W.  A. 
Beibl.  .9,  520. 

5  Publ.  d.  Astrophys.  Obs.  zu  Potsdam  (1886),  5. 

6  Photographic   Map  of   the   normal    Solar    Spectrum,   Johns    Hopkins 
Univ.,   Baltimore.     Astronomy  and  Astrophysics  (1893),  12,   321.      P.   M. 
(1894)  [5]  36,  49. 

7  N.  A.  $.  U.  (1868)  [3]  6. 

8  P.  T.  (1862)  152,  861. 

9  P.  T.  (1873)  163,  253,  639;  (1874)  164,  479,  805.     P.  R.  S.  25,  546;  27, 
49,  279,  409;  28,  157. 


8  SPECTRUM  ANALYSIS. 

subject,  but  he  soon  quitted  it,  and  its  fuller  examination  was 
reserved  for  Hartley  and  Adeney,1  and  Liveing  and  Dewar." 

Since  1888  Kayser  and  Runge3  have  met  with  great  suc- 
cess in  their  important  task  of  measuring  the  emission-spectra 
of  terrestrial  substances  by  Rowland's  method.  They  com- 
menced the  work  in  order  to  determine  the  relationship  of 
the  various  lines  of  an  element,  and  also  that  of  the  lines  of 
different  elements.  Attempts  had  been  made  in  this  direction 
shortly  after  the  discovery  of  spectrum  analysis  by  Kirchhoff 
and  Bunsen;  it  was  at  first  believed  that  the  relationship  of 
the  lines  was  similar  to  the  sound-waves  of  a  vibrating  string, 
which  consist  of  a  fundamental  note  and  harmonic  overtones. 
This  view  was  shown  by  Schuster4  in  1880  to  be  incorrect, 
and  in  1885  Balmer5  discovered  a  formula  which  accurately 
reproduces  the  hydrogen  lines  in  wave-lengths.  These  inves- 
tigations, together  with  the  observations  of  Liveing  and 
Dewar6  on  harmonic  series  of  similar  lines,  are  naturally  con- 
nected with  Kayser  and  Runge's  work,  which  has  led  to  the 
discovery  of  the  methodical  structure  of  a  series  of  spectra. 
Rydberg,7  working  independently  of  Kayser  and  Runge,  has 
obtained  similar  results.  Investigations  of  this  nature  have 
tended  to  greatly  widen  the  domain  of  spectrum  analysis. 

BIBLIOGRAPHY   OF    WORKS    ON    SPECTRUM    ANALYSIS. 

CAPRON.      Photographed  Spectra.  1877. 

CAZIN.      La  spectroscopie.      Paris,  1878. 
DEMARgAY.      Spectres  electriques.      Paris,  1895. 

DlBBlTS.      De  Spectraal-Analyse.  Rotterdam,  1869. 


P.  T.  1884,  p.  63. 

P.  T.  174.  187.     P.  R.  S.  34,  119,  123.     W.  A.  Beibl.  6,  934;  7,  849. 

A.  B.  A.  1888-1894.     Runge  B.  A.  R.  1888,  576. 

B.  A.  R.  1880. 
W.  A.  (1885)25. 

P.  T.  (1883)  174,  208. 

C.  r.  (1890)  110,  394.     K.  Vetenskaps  Akad.   Handl.,  23  (Stockholm, 
1890). 


INTRODUCTORY.     HISTORICAL.  9 

DIETERICI.  Spectralanalyse  in  Ladenburg's  Handworter- 
buch  der  Chemie.  Breslau,  1892. 

DRAPER.      Catalogue  of  Stellar  Spectra.      Cambridge,   1895. 

GANGE.      Die  Spectralanalyse.      Leipzig,   1893. 

DE  GRAMONT.  Analyse  spectrale  directe  des  mineraux. 
Paris,  1895. 

GRANDEAU.  Instruction  pratique  sur  1'analyse  spectrale. 
Paris,  1863. 

HiGGS.  Photographic  Atlas  of  the  Normal  Solar  Spectrum, 
1894. 

HUGGINS.  Results  of  Spectrum  Analysis  applied  to  the 
Heavenly  Bodies.  London,  1870. 

KAYSER.  Lehrbuch  der  Spectralanalyse.  Berlin,  1883. 
(Contains  measurements  of  spectra  and  a  very  complete 
review  of  the  literature.) 

Spectralanalyse  in  Winkelmann's  Handbuch  der  Physik 
(Encyclopedic  der  Naturw.).      Breslau,  1894. 

KLINKERFUES.  Die  Spectralanalyse  und  ihre  Anwendung 
in  der  Astronomic.  Berlin,  1879. 

V.  KOVESLIGETHY.  Grundzuge  einer  theoretischen  Spectral- 
analyse. Leipzig,  1890. 

KONKOLY.     Handb.  der  Spectroskopiker.     Halle  a.  S.,  1890. 

G.  AND  H.  KRUSS.  Colorimetrie  und  quant.  Spectralanalyse. 
Hamburg  and  Leipzig,  1891. 

LECOQ  DE  BoiSBAUDRAN.      Spectres  lumineux.     Paris,  1874. 

LlELEGG.      Die  Spectralanalyse.      Weimar,  1867. 

LOCKYER.      The  Spectroscope  and  its  Use.      London,  1874. 
-  Studies  in  Spectrum  Analysis.      New  York  and    Lon- 
don. 1878, 

LORSCHEID.     Die  Spectralanalyse.      Munster,  1875. 

MACMUNN.      The  Spectroscope.      London,  1888. 

PROCTOR.     The  Spectroscope.      London. 

ROSCOE.  Spectrum  Analysis.  Fourth  edition,  revised  by 
the  author  and  A.  Schuster.  London,  1885.  (Con- 
tains popular  lectures  on  the  subject  supplemented  by 


10  SPECTRUM  ANALYSIS. 

extracts  from  the  more  important  original  memoirs, 

and  a  good  bibliography.) 
SALET.     Traite    elementaire  de   spectroscopie,    I.  Fascicule. 

Paris,  1888. 
SCHEINER.       Die    Spectralanalyse    der    Gestirne.       Leipzig, 

1890.      (Contains  a  comprehensive  bibliography.) 
SCHELLEN.      Die  Spectralanalyse  in  ihrer  Anwendung  auf  die 

Stoffe  der  Erde   und  die  Natur  der  Himmelskorper. 

Braunschweig,    1883.      English   translation  by  J.   and 

C.  Lassel  edited  by  W.  Huggins.      New  York,  1872. 
SECCHI.     Die  Sonne,   German  by  Schellen.      Braunschweig, 

1872. 
THALEN.      Spectralanalyse    expose   och    Historick,    med    en 

Spectralkarta.      Upsala,  1866. 
TUCKERMAN.      Index  to  the  Literature  of  the   Spectroscope. 

Washington,   1888. 

VlERORDT.     Anwendung  des  Spectralapparates  zur    Photo- 
metric und  zur  quant.  Analyse.      Tubingen,   1873. 
VOGEL  H.   W.      Prakt.     Spectralanalyse     irdischer     Stoffe. 

Berlin,    1889.      (Deals  chiefly  with  practical  analysis, 

and  particularly  with  absorption-spectra.) 
WATTS.      Index  of  Spectra.      Manchester,   1889.      (Contains 

complete    measurements    of   spectra   and   a   very   full 

bibliography.      Supplements  to  the  index  appeared  in 

the  B.  A.  R.,  London.) 
YOUNG.     The  Sun.      New  York  and  London,  1897. 

See  also  text-books  on  physics,  amongst  others:  A. 
Lommel,  Lehrb.  d.  Experimentalphysik  (Leipzig,  1893); 
Muller-Pouillet's  Lehrb.  d.  Physik,  9.  Aufl.  v.  Pfaundler 
(Braunschweig,  1894);  Winkelmann,  Handb.  d.  Physik 
(Breslau,  1893);  Kelvin  &  Tait,  Elements  of  Natural  Philos- 
ophy; Tait,  Light;  Tyndall,  On  Light;  Wright,  Light. 


CHAPTER    II. 
PHYSICAL    PROPERTIES   OF    LIGHT.1 

ACCORDING  to  Huygens'  universally  accepted  theory, 
light  consists  of  wave-motions  of  the  ether,  the  vibrations 
being  transmitted  from  particle  to  particle  with  an  extremely 
high  velocity  in  straight  lines;  the  vibrations  of  the  particles 
of  ether  are  at  right  angles  to  the  path  of  the  ray.  On 
account  of  the  great  elasticity  of  the  ether,  and  the  ease  with 
which  the  vibrations  are  further  propagated,  single  rays  can- 
not be  obtained,  but  only  pencils  consisting  of  a  number  of 
rays,  which  may  be  considered  to  be  parallel  if  it  is  assumed 
that  the  vibrations  are  very  small,  or  at  a  great  distance  from 
the  source.  The  varying  frequency  of  the  vibrations  produces 
in  the  eye  the  effect  of  color;  the  number  of  vibrations  is 
constant  for  each  color,  but  in  a  given  medium  the  wave- 
length differs.  Since  all  light-rays  are  transmitted  with  a 
uniform  velocity  in  the  free  ether  or  in  a  vacuum,  and  almost 
so  in  air,  the  number  of  vibrations  is  small  or  great  in  propor- 
tion as  the  waves  are  long  or  short. 

Wave-length. — It  is  possible  to  directly  determine  the 
wave-length  corresponding  with  a  given  color  in  air,  and  it  is 
found  that  at  the  extremity  of  the  visible  red  the  wave-length 
(A)  of  the  ^4 -line  =  0.00076  mm.,  that  of  the  yellow  ^,-line 
=  0.000589  mm.,  and  that  of  the  AT-line  at  the  limit  of  the 
visible  violet  =  0.00039  mm.  The  velocity  (v)  of  light  is 


1  Comp.  Fehling-Hell's  Handworterbuch,  4,  87,  and  text-books  of  Phy- 
sics. 


12  SPECTRUM  ANALYSIS. 

known  to  be  about  300,000  kilometres  per  second;  the  num- 
ber of  vibrations  (»)  is  obtained  by  the  expression  n  = 

In  this  manner  it  is  found  that  the  number  of  vibrations  of 
the  above  three  lines  =  395,  509,  and  763  billions  per  second 
respectively.  These  numbers  are  inconceivably  great,  and 
awkward  to  write,  and  it  is  therefore  usual  to  define  the  color 
by  the  wave-length,  although  this  varies  with  the  medium. 
In  dealing  with  wave-lengths  measured  in  a  vacuum,  the 
millionth  part  of  a  millimetre  =  o.ooi  mikron  is  taken  as  the 
unit,  and,  in  accordance  with  Kayser's  suggestion,  it  is  repre- 
sented by  the  symbol  /*/*;  a  tenth  part  of  this  =  o. !////  is 
termed  an  Angstrom's  unit. 

Reflection. — The  light  which  falls  on  a  rough  nonlumin- 
ous  body  is  partly  absorbed  or  transmitted  and  the  remainder 
thrown  back  on  all  sides,  thus  making  the  object  visible;  but 
smooth  polished  surfaces — mirrors — only  reflect  the  light  in 
certain  definite  directions;  the  perpendicular  produced  at  the 
point  of  the  reflecting  surface  where  the  ray  impinges  is  in  the 
same  plane  as  the  incident  and  reflected  ray,  and  both  form 
identical  angles  with  it. 

Refraction. — The  passage  of  light  from  one  medium  to 
another — for  instance,  from  air  into  water  or  glass — causes  a 
part  of  it  to  be  thrown  back  in  accordance  with  the  law  of 
reflection,  whilst  the  remainder  traverses  the  new  medium,  but 

not  in  a  straight  line;  its  path  is 
deflected  (Fig.  i),  a  process  which  is 
known  as  refraction.  The  incident 
ray  ae  and  the  refracted  ray  eb  are  in 
the  same  plane  as  trie  normal  ed  of 
the  new  medium;  if  the  light  passes 
from  a  rare  to  a  denser  medium,  the 
FlG-  *•  refracted  ray  approaches  the  perpen- 

dicular, otherwise  it  recedes  from  it.  In  order  that  refraction 
may  take  place  the  incident  ray  must  form  an  acute  angle 


PHYSICAL   PROPERTIES   OF  LIGHT.  13 

with  the  normal;  if  it  forms  a  right  angle,  it  traverses  the 
medium  in  a  straight  line.  Every  incident  jjngle  corresponds 
with  a  particular  refractive  angle;  the  sine  ac  of  the  incident 
angle  i  bears  a  definite  relationship  ;/  to  the  sine  bd  of  the 
angle  of  refraction  r,  in  accordance  with  Snell's  law,  so  that 


sin  i  sin  i 

n  = or  sin  r  =  or  sin  i  =  n  sin  r. 

sin  r  n 


This  relationship  is  termed  the  refractive  index,  or  coeffi- 
cient of  refraction,  and  differs  for  every  transparent  substance. 
The  refractive  indices  of  the  following  substances  are  for 
/Might,  and  at  a  temperature  of  20°: 

Water   1.3333 

Alcohol , 1.3616 

Carbon  bisulphide 1 .6276 

tf-Bromonaphthalene 1.6582 

Ethylic  cinnamate  (at   18.8°) 1.5607 

Crown  glass 1.5  15-1.615 

Flint  glass   1.614-1.762 

Jena,  heaviest  silicate  flint  glass,  No.  557 1.9625 

Quartz  (ordinary  ray) 1 .5442 

Fluor-spar 1.4339 

Air  (o°  and  760  mm.) 1.0002922 

Plates  with  plane  parallel  surfaces  cause  the  incident  ray 
to  be  as  much  deflected  towards  the  perpendicular  as  the  issu- 
ing ray  is  bent  from  it;  the  two  rays  are  therefore  parallel  to 
one  another. 

Prisms. — A  prism  is  a  wedge-shaped  transparent  object 
with  two  polished  surfaces  forming  an  angle  with  one  another. 
The  section  of  an  ordinary  simple  glass  prism  forms  an  equi- 
lateral triangle  (Fig.  2);  the  polished  sides  AB  and  AC  are 
the  refracting  surfaces,  enclosing  the  refracting  angle  a  and 


14  SPECTRUM  ANALYSIS. 

forming  the  refracting  edge  A.     If  a  ray  of  light  in  the  plane 

of  the  section  falls  on  one  of 
the  sides  AB  or  AC,  it  is  bent 
at  its  entrance  and  exit,  in  ac- 
cordance with  the  law  of  refrac- 
tion, and  approaches  the  thick 
portion  of  the  prism.  The  ex- 
tent of  this  deflection  is  equal 
to  the  angle  d  which  the  incident 

FIG.  a.  .  r  •   i 

and  issuing  rays  torm  with  one 

another,  and  is  also  equal  to  the  sum  of  the  angle  of  incidence 
and  that  of  the  issuing  ray,  minus  the  refractive  angle.  The 
angles  /',  r,  and  a  bear  a  certain  interrelationship,  and  it  is 
possible  to  calculate  in  what  position  of  the  prism  the  refrac- 
tion will  be  smallest;  this  can  be  confirmed  by  direct  observa- 
tion. This  minimum  deviation  occurs  when  the  ray  forms  the 
same  angle  with  the  refracting  surfaces  externally  and  inter- 
nally, or,  in  other  words,  when  it  traverses  the  prism  sym- 
metrically. The  refractive  index  n  of  the  material  of  which 
the  prism  is  composed  may  be  calculated  by  the  expression 

_  sin  \(d -\-  a) 

fir      '  "  .  1  » 

sm  \a 

the  minimum  deviation  and  angle  of  refraction  being  measured 
by  means  of  the  goniometer. 

Dispersion. — Refraction  not  only  changes  the  direction 
of  a  ray  of  light,  but,  if  it  is  not  homogeneous,  its  nature  is 
also  modified;  a  ray  of  white  light  is  converted  into  a  rain- 
bow-colored band,  as  may  be  easily  seen  by  the  help  of  a 
prism.  The  polychromatic  rays  composing  white  light  are 
transmitted  with  uniform  velocity  in  a  vacuum,  but  in  a 
denser  medium  the  more  rapidly  vibrating  violet  rays  undergo 
a  greater  retardation  than  the  red  rays,  which  vibrate  more 
slowly;  the  former  are  therefore  refracted  more  strongly  than 


PHYSICAL   PROPERTIES   OF  LIGHT.  15 

the  latter.  The  component  rays  are  more  strongly  refracted 
by  passage  through  a  second  prism,  but  do  not  undergo  any 
further  decomposition;  they  are  therefore  simple  or  homo- 
geneous, and  if  combined  by  means  of  a  lens  white  light  is 
reproduced. 

These  experiments,  which  are  of  fundamental  importance 
both  for  spectrum  analysis  and  for  the  theory  of  light,  were 
first  performed  by  Newton  in  1668,  and  described  in  his 
44  Opticks  "  in  1675.  He  allowed  a  ray  of  sunlight  to  pass 
through  a  small  hole  in  a  window-shutter  into  a  darkened 


FIG.  3. 


room  XY  (Fig.  3);  he  passed  the  rays  through  a  prism  ABC, 
which  caused  them  to  be  deflected  and  resolved  into  the 
colored  band  PT,  which  he  termed  a  spectrum,  and  which 
was  received  on  the  white  screen  MN.  The  colored  rays 
when  viewed  by  Newton  through  a  second  prism  gave  the 
impression  of  white  light,  but  when  they  were  made  to 
traverse  it  separately  they  were  not  further  decomposed,  but 
only  underwent  a  second  refraction. 

Abnormal  Dispersion. — The  refractive  index  of  a  medium 
is,  as  a  rule,  greater  the  smaller  the  wave-length  of  the  par- 
ticular light;  in  the  visible  spectrum  the  index  steadily 
increases  in  passing  from  red  to  blue.  Certain  substances  do 
not  conform  to  this  rule,  their  solutions,  when  employed  as 
refracting  and  dispersing  agents,  exhibit  the  inverse  relation- 


1 6  SPECTRUM  ANALYSIS. 

ship  between  refractive  index  and  dispersion.     This  phenome- 
non is  termed  abnormal  dispersion.1 

Pure  Spectra. — The  colors  obtained  if  the  light  is  ad- 
mitted to  the  prism  through  a  round  opening,  as  in  Newton's 
experiment,  are  never  completely  separated  from  one  another, 
as  the  circular  shape  of  the  images  causes  them  to  overlap. 
In  order  to  separate  the  various  colors  as  completely  as  possi- 
ble, and  obtain  a  pure  spectrum,  a  narrow  longitudinal  slit 
has,  since  Wollaston's2  time,  been  generally  employed  for  the 
admission  of  the  light.  The  number  of  images  of  the  slit 
produced  is  equal  to  that  of  the  different  wave-lengths  in  the 
light  employed,  and  consequently  the  narrower  the  slit  the 
less  do  the  images  superpose;  the  spectrum  thus  obtained  may 
be  magnified  to  any  desired  extent.  The  resolving  power  of 
a  prism,  or  system  of  prisms,  is  partly  dependent  on  its  dis- 
persion, but  to  a  greater  extent,  as  Rayleigh  3  has  shown,  on 
the  distance  which  the  ray  traverses  in  its  route  through 
them.  The  thickness  of  heavy  flint  glass  required  to  separate 
the  ZMines  —  1.02  cm.;  taking  this  value,  roughly  i  cm.,  as 
unit,  the  resolving  power  of  a  prism  of  similar  glass  in  the 
region  of  the  ZMine  is  equal  to  its  thickness  in  centimetres; 
in  other  parts  of  the  spectrum  it  is  inversely  proportional  to 
the  cube  of  the  wave-length,  so  that  it  is  eight  times  greater 
in  the  violet  than  in  the  red,  and  therefore  corresponds  with 
the  total  thickness,  or  with  the  length  of  the  base  of  the  prism 
or  system,  but  is  independent  of  the  number  of  prisms,  of 
their  angle,  or  of  the  order  in  which  the  various  members  of 
the  system  are  arranged. 

Gratings. — An  optical  grating  consists  of  a  plate  with  a 
large  number  of  parallel  lines  ruled  upon  it ;  this  arrangement, 

1  Christiansen,   P.  A.  (1870)  141,  479;  (1871)  143,  250.       Kundt,   P.  A. 
(1871)  143,  259;  144,   128;  (1872)  145,  67.       Sieben,  W.   A.   (1879)  8,    137. 
Sellmeier,  P.  A.  145,  396,  520;  147,  386,  525.     H.   v.   Helmholtz,  Monats- 
ber.  Berl.  Akad.  (1874),  p.  667.     P.  A.  (1874)  154,  582. 

2  P.  T.  (1802)  p.  378. 

»  P.  M.  (1879)  [5]  9,  269. 


PHYSICAL   PROPERTIES    OF  LIGHT.  If 

like  a  prism,  produces  spectra.  Gratings  were  first  employed 
by  Fraunhofer,1  who  at  first  used  a  wire  grating  prepared  by- 
winding  thin  wire  over  two  similar  screws  of  very  fine  thread, 
placed  parallel  to  one  another;  later  he  engraved  numerous 
fine  lines,  closely  adjacent  and  at  regular  intervals,  on  gold- 
leaf  backed  by  glass,  and  finally  employed  glass  plates  with 
opaque  lines  cut  by  means  of  a  diamond.  The  preparation 
of  gratings  has  been  greatly  improved  in  more  recent  times 
by  the  use  of  good  dividing-machines.  Two  kinds  of  gratings 
are  made,  the  transparent  ones  of  glass,  with  as  many  as  800 
lines  per  mm.,  and  reflection  gratings  of  speculum  metal  which 
reflects  instead  of  transmitting  the  light;  the  latter  are 
preferable  for  spectroscopic  work,  as  less  light  is  absorbed. 
Rutherfurd,  in  the  United  States,  considerably  improved  the 
construction  of  the  reflection  grating,  and  since  1882  their 
preparation  has  been  carried  to  an  extraordinarily  high  degree 
of  perfection  by  Rowland  at  Baltimore.  His  plane  and  con- 
cave gratings  with  10,000,  14,438,  and  20,000  lines  per  inch 
are  almost  faultless,  and  comparatively  free  from  scratches 
caused  by  irregularity  of  the  diamond-point  (Ghosts). 

Diffraction. — When  a  narrow  illuminated  slit  is  viewed 
through  a  glass  grating,  the  lines  of  which  are  parallel  with 
the  edges  of  the  slit,  a  bright  image  of  it  is  observed  with  a 
series  of  spectra  on  each  side;  the  violet  rays  with  the  shortest 
wave-length  are  nearest,  and  the  red  rays  most  distant,  from 
the  centre  in  each  spectrum,  and,  if  the  colors  are  almost 
equally  dispersed,  the  yellow  will  be  found  in  the  middle.  The 
spectra  are  distinguished  as  of  the  first,  second,  .  .  .  w/th 
order,  counting  from  the  centre.  The  spectra  of  the  first 
order  only  are  pure;  the  others  are  modified  by  the  superpos- 
ing of  other  spectra,  but  they  may  be  separated  by  means  of 
a  ^mall  prism  as  described  in  the  following  chapter.  The 
intensity  of  the  illumination  diminishes  with  ascending  order 
of  the  spectra. 

1  Denkschriften  d.  Miinchener  Akad.  (1822)  8.    Gilbert's  Ann.  74,  337. 


1 8  SPECTRUM  ANALYSIS. 

The  production  of  spectra  by  means  of  gratings  is  due  to 
diffraction;  part  of  the  light  traversing  the  spaces  between 
the  rulings  continues  in  a  straight  line,  but  a  portion  is  bent 
sideways,  or  refracted,  by  the  sharp  edges  of  the  opaque  parts. 
The  explanation  of  this  phenomenon  afforded  by  the  wave- 
theory  of  light  is  as  follows:  The  light-waves  which  fall  on  a 
fine  slit  cause  the  particles  of  ether  present  to  vibrate;  this 
motion  is  communicated  to  the  neighboring  particles  and  pro- 
duces an  equal  number  of  light-waves  which  reinforce,  weaken, 
or  neutralize  each  other,  in  accordance  with  the  law  of  interfer- 
ence. The  neutralization  occurs  in  all  directions  in  which  the 
difference  between  two  sets  of  waves  is  other  than  a  whole 
wave-length.  In  the  case  of  white  light,  diffracted  by  means 
of  a  grating,  the  image  of  the  slit,  in  the  middle,  is  white 
because  at  this  point  all  the  colors  are  superposed,  but  the 
colored  rays  which  differ  in  phase  by  one  wave-length  collect 
at  each  side  according  to  their  wave-lengths,  and  form  a 
spectrum  of  the  first  order;  those  rays  with  a  greater  differ- 
ence of  phase  forming  the  spectra  of  the  second,  third,  .  .  . 
mth  order. 

The  wave-length  may  be  determined,  if  the  distance 
between  the  lines  of  the  grating  is  known,  by  measuring  the 
angle  of  diffraction  with  a  gonimeter.  Angstrom  in  this 
manner  found  the  following  values,  in  ten  millionths  of  a  milli- 
metre, for  the  Fraunhofer  lines  given: 

A      B      C      D,      E      F      G      H 
7604   6867   6563   5895    5269   4861   4307   3968 

The  dispersive  power  of  a  grating  is  dependent  on  the 
total  number  of  the  spaces  into  which  it  is  divided,  and  on 
the  order  of  the  spectrum;  in  one  of  the  first  order  1000  lines 
per  inch  are  necessary  to  separate  the  ZMines,  whilst  a  large 
Rowland  grating,  in  a  spectrum  of  the  first  order,  is  capable 
of  dividing  two  lines  differing  in  wave-length  by  only  0.05  of 
an  Angstrom. 


UNIVERSITY 


PHYSICAL   PROPERTIES   OF  LIGHT.  1  9 

Comparison  of  the  Diffraction  and  Refraction  Spectra. 

—  Diffraction  spectra  differ  from  those  produced  by  refraction 
in  the  dispersion  of  the  rays  being  proportional  to  the  wave- 
length, and  this  uniform  extension  applies  although  the  dis- 
persion increases  with  the  number  of  lines  on  the  grating. 
The  refraction  in  the  case  of  a  prism  spectrum  increases  with 
diminishing  wave-lengths;  the  violet  and  blue  rays  are  there- 
fore comparatively  widely  separated,  and  the  red  ones  gath- 
ered together.  The  length  of  the  spectrum  is  also  influenced 
by  the  composition  of  the  prism,  so  that  results  obtained  with 
different  spectroscopes  are  not  directly  comparable;  diffractive 
spectra  are  therefore  taken  as  typical  or  normal,  and  all  scale 
readings  with  a  prism  spectroscope  are  reduced  to  wave- 
lengths. The  prism  spectrum  has  the  advantage  over  the 
diffraction  spectrum  of  greater  brightness,  only  a  small  pro- 
portion of  the  light  is  lost  by  reflection  and  absorption, 
whereas  with  the  grating  a  portion  of  the  light  passes  through 
without  being  diffracted,  a  portion  is  weakened  by  interfer- 
ence, and  the  remainder  is  divided  amongst  a  number  of 
spectra  instead  of  being  concentrated  into  one  as  in  the  case 
of  the  prism.  The  prism  spectrum  is  therefore  employed 
where  the  illumination  is  comparatively  feeble,  the  grating 
being  used  for  intense  light  and  in  cases  where  a  high  dis- 
persion is  necessary.  A  large  Rowland  grating  in  the  region 
of  the  ZMine  produces  the  same  effect  as  a  prism  126  cm.  in 
thickness;  in  the  violet  this  proportion  changes  in  favor  of  the 
prism  ;  at  A  —  2000  the  same  separation  is  attained  by 
means  of  a  prism  only  4  cm.  in  thickness. 


CHAPTER    III. 
SPECTROSCOPES. 

THE  numerous  forms  of  instruments  for  spectrum  analysis 
are  all  divisible  into  two  classes,  prism  spectroscopes '  with 
angular  or  direct  vision,  and  grating  spectroscopes.3  The 
forms  vary  according  to  the  special  purpose  for  which  the 
instrument  is  to  be  employed,  such  as  exact  measurements, 
quantitative  and  photometrical  investigations,  microscopical 
or  astronomical  observations,  or  for  the  preparation  of  spec- 
troscopic  photographs. 

Prism  Spectroscope  with  Angular  Vision. — The  appa- 
ratus employed  by  Kirchhoff  and  Bunsen 3  in  their  earlier 
investigations  is  shown  in  Fig.  4.  It  consists  of  a  hollow 
glass  prism  F  filled  with  carbon  bisulphide,  of  a  telescope  C 
magnifying  eight  times,  and  of  the  slit  tube  or  collimator  B, 
at  the  end  nearest  to  the  light;  this  is  closed  with  a  plate 
pierced  with  a  fine  slit;  the  other  end  contains  a  lens  which 
makes  the  light-rays  coming  from  D  parallel  before  they  fall 
on  the  prism.  Shortly  afterwards  Steinheil  of  Munich  con- 

1  For  information  on  the   theory  of  the  prism  in   the   spectroscope  see 
Reusch,  P.  A.  (1862)  117,  241.       Pickering,  Sillim.  Journ.  (1868)  45,  301. 
Christie,  P.  R.  S.  (1877)  26,  9.    Thollon,  Journ.  de  phys.  d'Almeida  (1878), 
7,  141. 

2  For  the  theory  of  gratings  see   Rowland,  P.  M.   (1892)  [5]  13;   16,  197. 
Astronomy  and  Astrophysics  (1893),  12,  129.     Ames,  Johns  Hopkins  Univ. 
Circular  (1889),  8,  No.   73,    p.  69.     P.   M.  (1889)  [5]  27.     Runge,  Winkel- 
mann's  Handb.  d.  Phys.  (Breslau,  1894),  p.  407.     Glazebrook,  P.  M.  (1889) 
[5]  27.     Mascart,  Journ.  d.  phys.  d'Almeida  (1883)  [2]  2.     Lord  Rayleigh, 
P.  M.  (1874)  [4]  47. 

3  Chem.  Analyse  durch  Spectralbeobachtungen,  P.  A.  110,  167. 


SPECTROSCOPES. 


21 


structed  for  them  an  improved  form  of  spectroscope  (Fig.  5) 
which  is  still  in  use.  A  flint-glass  prism  P  of  60°  is  fastened 
to  a  cast-iron  stand  which  also  carries  the  collimator-tube  A, 


FIG.  4. 


FIG.  5. 


the  telescope  B,  and  the  telescope  C  containing  a  scale.  The 
mechanism  for  producing  the  slit  carried  by  the  collimator- 
tube  is  shown  enlarged  in  Fig.  6.  The  width  of  the  slit  can 


22 


SPECTRUM  ANALYSIS. 


be  regulated  by  a  micrometer-screw;  on  the  lower  end  a  small 
reflecting  prism  (Fig.  7)  is  fixed,  by  means  of  which  a  second 
source  of  light,  placed  at  the  side,  may  be  examined  together 
with  the  first.  With  the  apparatus  arranged  as  in  Fig.  '5 
the  spectrum  of  the  flame  F  appears  above  that  of/,  so  that 
it  is  possible  at  a  glance  to  see  whether  the  former  contains 
the  substance  sought,  if  a  specimen  of  it  is  simultaneously 
volatilized  in  the  latter.  A  millimetre  scale  5  is  contained  in 
the  tube  C\  it  is  illuminated  by  a  small  luminous  flame,  and 


FIG.  6. 


FIG.  7. 


its  image  reflected  by  the  adjacent  side  of  the  prism  into  the 
telescope  B.  In  order  to  prepare  such  a  spectroscope  for  use, 
the  telescope  B  is  detached,  and  adjusted  to  infinity  by 
observing  some  fixed  object  at  a  considerable  distance;  if  it 
contains  cross-wires,  these  must  be  first  focussed  with  the  eye- 
piece; the  telescope  is  then  replaced,  and  the  slit  opened  so 
that  the  spectrum  lines  are  sharply  defined,  until,  for  instance, 
the  sodium  lines  are  resolved,  and  the  scale-tube  is  drawn  out 
to  make  the  divisions  clearly  visible.  In  many  modern  instru- 
ments the  length  of  the  tubes  A  and  C  is  adjusted  to  their 
lenses  before  they  are  sent  out,  so  that  only  the  eyepiece 
requires  focussing  by  each  individual  observer. 

The  clearness  of  a  spectrum  is  considerably  influenced  by 
the  slit  apparatus.  The  manufacture  of  these  has  greatly  im- 
proved in  the  course  of  time,  in  finish,  in  the  opening 
mechanism,  and  in  the  permanency  of  the  material  employed; 
the  best  substance  for  the  edges  is  quartz,  but  platinum  or 
brass  is  generally  used. 


The  spectroscope  above  described  is  suitable  for  chemical 
laboratories,  but  not  for  astronomical  purposes,  for  which  a 
greater  dispersion  is  necessary;  this  may  be  obtained  by  the 
use  of  several  prisms  instead  of  one.  The  instrument  made 
by  Steinheil,  and  used  by  Kirchhoff  in  preparing  his  draw- 
ings of  the  solar  spectrum,  is  shown  in  Fig.  8.  It  contains 


FIG. 


four  prisms,  and  is  at  once  simple  and  sensitive.  The  prisms 
are  of  flint  glass  with  angles  of  60°,  45°,  45°,  45°;  the  light 
traverses  them  successively,  and  is  refracted  through  130°,  so 
that  the  spectrum  is  greatly  extended.  The  telescope  B 
enlarges  36  and  72  times,  according  to  the  lenses  employed, 
and  moves  on  a  divided  circle  by  means  of  a  micrometer-screw 
R\  with  the  help  of  the  cross-wires  the  distance  between  two 
lines  may  be  readily  measured;  the  slit  is  regulated  by  a 
sliding  micrometer,  and  is  provided  with  a  comparison-prism. 
The  measurements  may  also  be  made  with  an  illuminated 
scale  in  a  second  telescope  (not  shown  in  the  figure);  this  is 
sometimes  inconvenient,  as  the  spectrum  is  so  much  longer 


24 


SPECTRUM  ANALYSIS. 


than  the  scale  that  the  latter  requires  frequent  readjustment. 
In  the  above  instrument  the  prisms  are  moved  by  hand  into 
the  position  of  minimum  dispersion  for  any  given  color;  this 
is  unsatisfactory:  the  arrangement  devised  by  Browning 
(Fig.  9)  makes  the  adjustment  automatic.  The  prisms  are 


FIG.  o. 

connected  to  each  other,  and  to  the  observation-telescope,  by 
hinges,  and  are  fixed  on  metal  plates  the  other  ends  of  which 
are  suitably  cut  to  receive  a  central  screw ;  on  rotating  the 
telescope  B  to  any  particular  line  in  the  spectrum,  the  prisms 
move  with  it,  so  that  the  ray  traverses  then  symmetrically. 
Gassiot's  spectroscope,  constructed  by  Browning  on  this  plan, 
contained  nine  prisms  and  possessed  high  refractive  power. 

There  are  several  other  ways  by  which  the  dispersion  may 
be  increased;  instead  of  using  several  prisms  the  light  may  be 
repeatedly  passed  through  a  single  one,  or  hollow  prisms  filled 
with  some  liquid  of  high  refractive  power  may  be  employed. 


SPECTROSCOPES. 


Acting  on  a  suggestion  of  Littrow,1  Grubb,1  C.  A.  Young, 
and  Lockyer  caused  the  light  to  pass  twice  through  the  same 


FIG.  10. 


prism,  as  shown  in  Fig.  10.  The  ray  passes  first  through 
the  upper  part  of  the  prism  and  is  then  returned  through  the 
lower  portipn  by  means  of  a  reflecting  prism.  The  instru- 
ment shown  is  made  by  Browning;  it  is  extremely  powerful, 
and  suitable  both  for  laboratory  and  stellar  work.  It  contains 
six  prisms,  besides  the  reflecting  prism,  and  consequently  the 
dispersive  power  is  equal  to  that  of  twelve  prisms.  The  posi- 
tion of  any  one  prism  can  be  altered  at  will,  without  interfer- 
ence with  the  other  parts  of  the  instrument,  so  that  the 
dispersive  power  can  be  readily  changed  from  two  up  to 
twelve  prisms  as  required.  The  adjustment  of  the  prisms  to 
the  position  of  minimum  dispersion  is  made  automatically  in 


1  Wien.    Her    47,  2,  p.  26. 

8  Monthly  notices  of  the  Roy.  Astron.  Soc.  30,  36. 


26 


SPEC TR  UM  A NA  L  YSIS. 


the  manner  described  above;  the  position  of  the  spectrum- 
lines  is  measured  by  means  of  a  micrometer-screw,  the  move- 
ment of  which  also  adjusts  the  prisms.  Hilger  of  London 
constructed  a  large  spectroscope  in  which  the  ray  of  light  was 
passed  six  times  through  the  same  prism.  The  application 
of  this  method,  and  also  the  number  of  prisms  which  can  be 
employed,  is  limited;  the  longer  the  spectrum  the  less  bright 
any  given  portion  must  necessarily  be.  Moreover,  the  glass 
of  which  the  prisms  are  composed  is  never  absolutely  homo- 
geneous, nor  the  faces  perfectly  true;  hence  when  many 
prisms  are  used  there  is  a  loss  of  clearness  and  definition. 
Ordinary  prisms  are  greatly  surpassed  in  dispersive  power  by 
the  compound  prism  of  Browning  and  of  Rutherfurd,1  which 
bears  the  name  of  the  latter.  It  consists  of  a  flint-glass  prism 


FIG 


with  its  faces  at  such  an  angle  that  light  which  enters  cannot 
emerge;  in  order  to  permit  this,  compensating  prisms  of  crown 
glass,  and  therefore  with  a  lower  dispersive  power,  are 
cemented  to  each  side  face.  This  use  of  crown  glass  has 
(Comparatively  little  effect  on  the  dispersion. 

vThollon 2  constructed  an  instrument  which,  whilst  probably 

1  Sillim.  Journ.  (1865)  [3]  35,  71,  407. 

2  C.  r.  36,  329,  395,  595;  88,  So;  89,  749. 


SPECTROSCOPES.  2J 

unsurpassed  in  dispersive  power,  contains  only  a  small  number 
of  prisms  (Fig.  1 1).  Its  efficiency  is  due  partly  to  careful 
calculation  of  the  most  suitable  angles  for  the  faces  of  the 
prisms,  partly  to  their  being  filled  with  carbon  bisulphide, 
which  has  a  high  refractive  power  (comp.  preceding  chapter). 
Only  compound  prisms  are  used,  one 
of  which  is  shown  in  Fig.  12.  The 
refractive  angle  of  the  inner  flint- 
glass  prism  is  90°,  that  of  the  carbon 
bisulphide  prism  113°,  and  of  the  FIG.  12. 

crown-glass  prism  18  and  31°  respectively.  The  light  passes 
from  the  collimator  CBA  through  the  compound  prism  A 
(Fig.  13),  then  through  the  half-prism  B,  to  the  reflecting 


FIG.  13. 


prism  P\  it  now  returns  at  a  lower  level,  traversing  the  sym- 
metrically arranged  system  A  'B'P',  and  finally  emerges  below 
the  prism  A.  The  telescope  (E,  Fig.  u)  of  this  instrument 
is  fixed,  the  prisms  being  movable,  and  maintaining  the  posi- 
tion of  minimum  dispersion.  The  screw  F  serves  to  rotate 
the  prisms,  and  also  a  strip  of  paper,  such  as  is  used  in  the 
Morse  telegraph-instruments;  when  a  line  is  observed  at  the 
point  of  intersection  of  the  cross-wires  the  lever  D  is  pressed, 
causing  the  marker  to  record  the  position  on  the  paper. 
Prisms  containing  carbon  bisulphide  are  all  subject  to  the 
disadvantage  that  its  refractive  power  is  greatly  influenced  by 
temperature,  an  increase  of  o.  i°  C.  being  sufficient  to  alter 
the  position  of  the  lines  to  a  distance  equal  to  that  between 


28  SPECTRUM  ANALYSIS. 

the  two  sodium  ZMines.  It  is  therefore  necessary,  when 
using  such  prisms,  to  take  care  that  the  temperature  remains 
uniformly  constant.  To  accomplish  this,  Rayleigh,  and  also 
Draper,  employ  automatic  stirrers.  It  has  been  proposed  to 
replace  the  carbon  bisulphide  by  other  highly  refractive 
liquids;  Wernicke  has  suggested  ethylic  cinnamate,  and 
Walter  or-bromo-naphthalene  as  being  suitable  for  this  pur- 
pose. 

Direct-vision  Spectroscopes. — With  the  spectroscope 
last  described  the  emergent  ray  travels  at  an  angle  with  the 
entering  one;  instruments  in  which  the  slit,  lens,  prism,  and 
telescope  are  in  a  straight  line  are  termed  direct-vision  spec- 
troscopes. They  can  be  readily  attached  to  a  microscope  or 
telescope,  they  are  easy  to  handle  and  transport,  are  compara- 
tively cheap,  and  the  source  of  light  can  be  viewed  directly, 
so  that  these  advantages  over  the  ordinary  form  have  led  to 
their  wide  use  for  practical  purposes  where  a  great  dispersion 
is  not  required.  Amici  in  1860  constructed  a  compound 
prism  which  almost  permitted  of  direct  vision;  it  consisted  of 
a  flint-glass  prism  of  90°,  with  a  crown-glass  prism  on  each 
side;  Janssen  1  afterwards  made  a  more  elaborate  system  (Fig. 


FIG. 


14),  consisting  of  three  crown-  and  two  flint-glass  prisms, 
which,  whilst  resolving  the  ray  into  "its  constituents,  prevents 
its  deflection.  The  spectrum  from  a  flint-glass  prism  is 
almost  double  the  length  of  that  from  a  similar  one  of  crown 


1  C.  r.  55,  576. 


SPE  C  TROS  COPES. 


29 


glass,  so  that  the  dispersion  is  reduced  by  about  one  half  in 
consequence  of  refraction  in  the  opposite  direction.  It  is 
only  in  a  certain  definite  part  of  the  spectrum,  generally  the 
green,  that  the  incident  and  emergent  rays  follow  the  same 
path;  the  other  portions  are  deflected  to  each  side.  The 
spectroscope  constructed  by  Hofmann  of  Paris,  under  the 


FIG.  15. 

direction  of  Janssen,  is  shown  in  Fig.  15.  The  slit  S  of 
steel,  is  regulated  by  means  of  a  screw,  and  has  a  comparison- 
prism;  the  tube  P  contains  the  lens  E  and  a  compound  prism 
(Fig.  14);  it  is  attached  to  the  telescope  F,  which  can  be 
adjusted  to  any  portion  of  the  spectrum  by  the  screw  X. 
For  most  practical  purposes  a  telescope  is  unnecessary.  The 
instrument  (Fig.  16)  first  constructed  by  Browning  of  London 
is  very  convenient,  and  is  widely  used;  it  is  known  as  the 
direct-vision,  pocket,  or  miniature  spectroscope.  It  consists 


SPECTRUM  ANALYSIS. 


of  the  slit  S,  the  size  of  which  can  be  regulated  by  turning 
the  cap  s,  the  lens  C,  and  the  compound  prism  P,  composed 
of  four  crown-  and  three  flint-glass  prisms;  the  eyepiece  R 


FIG.  16. 


is  adjustable.      Another  form  of  the  same  instrument  (Fig. 
17),  also  made  by  Browning,  carries  a  detachable  comparison- 


FIG.  17. 


prism  and  a  photographed  micrometer-scale,  which,  together 
with  a  biconvex  lens,  is  contained  in  a  small  tube  fixed 
parallel  with  the  larger  tubs  by  a  slot  attachment;  a  reflection- 
prism  throws  the  image  of  the  scale  on  the  outer  surface  of 
the  last  member  of  the  compound  prism,  whence  it  is  reflected 
into  the  eye  of  the  observer.  The  instrument  is  only  8.5  cm. 
in  length,  and  when  in  use  is  attached  to  a  readily  adjustable 
stand.  Pocket  spectroscopes  similar  to  the  simpler  Browning 
form  are  manufactured  by  all  instrument-makers.  Guided  by 
H.  W.  Vogel,1  Schmidt  and  Haensch  of  Berlin  construct  an 
instrument  which,  instead  of  the  scale,  has  a  small  rotatable 
mirror;  the  light  from  this  is  projected  on  to  a  reflecting 
prism,  and  thence  to  the  upper  portion  of  the  slit.  The 
mirror  and  comparison  prism  can  be  readily  disconnected 


1  Ber.  9,  1645;  10,  1428. 


SPECTROSCOPES.  31 

The  majority  of  the  above  spectroscopes  give  a  field 
extending  only  from  the  A-  to  the  (9-line;  the  violet  portion 
is  almost  completely  absent.  Adam  Hilger  of  London  con- 
structs a  direct-vision  spectroscope  which,  whilst  somewhat 
longer  than  the  others,  is  characterized  by  a  high  dispersive 
power.  The  spectrum  extends  from  the  extreme  red  beyond 
the  //-line,  shows  the  two  /Mines,  and,  when  directed  at  the 
sun,  the  nickel  lines  between  them.  The  instrument  is  fitted 
with  an  achromatic  eyepiece,  and  a  special  arrangement  which 
reflects  a  slender  line  of  light  on  to  the  spectrum  to  serve  as 
a  means  of  measurement;  as  the  color  and  intensity  of  the 
line  can  be  regulated,  it  permits,  particularly  in  the  darker 
portions  of  the  spectrum,  of  far  more  accurate  determinations 
than  could  be  made  with  cross-wires.  The  measuring  is  per- 
formed with  the  help  of  a  micrometer-screw  attached  to  the 
slit,  which  it  moves  from  end  to  end  of  the  spectrum. 

Amongst  other  direct-vision  spectroscopes l  Christies' 2 
deserves  mention  on  account  of  peculiarities  in  its  construc- 
tion. He  employed  "half-prisms,"  which  are  so  called 
because  they  may  be  regarded  as  the  halves  of  a  tripartient 
compensating  prism;  the  refracting  angle  may  vary:  if  it  is 
90°,  a  long  enlarged  direct-vision  spectrum  is  obtained,  but 
the  dispersion  is  not  correspondingly  great,  and  the  illumina- 
tion is  poor.  Hitherto  it  has  only  been  used  in  England. 

Grating  Spectroscopes. — The  advantages  of  diffraction- 
spectra  have  been  already  numerated,  and  it  was  mentioned 
that  the  grating  spectroscope  can  only  be  used  where  the 
light  is  extremely  bright,  as  in  the  case  of  the  sun  and  elec- 
tric arc,  since  the  loss  of  light  is  considerable.  The  instru- 
ment is  usually  employed  in  the  form  of  a  spectrometer,  of 
which  one  variety  is  shown  in  Fig.  20.  The  gratings  are 
of  glass  or  metal,  the  latter  being  preferable  for  exact 

1  Alex.   Herschel,   Monit.   scientif.   7,  259.     Emsmann,   P.   A.   150,  636. 
Kessler,  P.   A.    151,  507.     Fuchs,  Zeitschr.  f.  Instrumentenkunde,  1,  352. 

2  P.  R.  S.  26.  8. 


SPE  C  TR  UM  A  NA  L  YSIS. 


work.      The  general  plan  of  a  spectrometer  is  shown  in   Fig. 
18.      The  grating  m   is  at  right    angles  with  the  collimator 

L,  and  secured  to  the  bed  of  the 
instrument;  the  telescope  F  is 
fitted  with  cross-wires,  and 
situated  at  right  angles  with  the 
axis  of  the  instrument.  The 
telescope  is  directed  towards 
the  slit  d,  and  its  position  read 
off  on  the  divided  circle;  homo- 
geneous light,  such  as  the  so- 
dium flame,  is  then  allowed  to 
fall  on  the  slit,  and  the  telescope 
rotated  until  the  spectra  of  the 
first,  second,  and  third  order 
are  successively  brought  into 
the  field  of  view,  each  position 
being  noted;  the  wave-length 
of  sodium  light  being  accurately 
known,  the  readings  provide  a 
means  of  measuring  the  wave- 
length of  any  other  kind  of 
light,  since  the  wave-length  of 
the  latter  bears  the  same  pro- 
portion to  that  of  sodium  light 
as  the  corresponding  scale  read- 
ings. The  wave-length  can  also  be  directly  determined  if 
the  grating-constant  is  known ;  this  is  effected  by  counting 
under  the  microscope  the  number  of  lines  in  I  mm.  It  was 

o 

with  such  an  instrument  that  Angstrom  made  his  celebrated 
determinations  of  the  lines  in  the  solar  spectrum. 

A  simple  form  of  spectroscope  with  a  reflex  grating  is 
shown  in  Fig.  19.  The  telescope  and  collimator  are  situated 
close  together  on  separate  mountings;  the  grating  is  enclosed 
in  a  case  with  a  plane  parallel  glass  front  to  protect  it  from 


FIG.  18. 


SPECTROSCOPES. 


33 


corrosive  fumes,  and  is  fixed  on  a  revolving  stand  so  that 
spectra  of  any  desired  order  can  be  brought  before  the  cross- 
wires  of  the  telescope.  The  spectra  of  higher  order  overlap,, 
but  they  may  be  easily  separated  by  following  Fraunhofer's 
suggestion,  and  placing  a  prism  between  the  grating  and  tele- 


FIG.  19. 

scope  in  such  a  position  that  the  plane  of  refraction  is  at  right 
angles  to  that  of  the  grating;  the  spectra  then  appear  clearly 
one  above  another,  and  can  be  separately  observed. 

Rowland's  Concave-grating  Spectroscope. — The  de- 
velopment of  spectrum  analysis  received  a  considerable  impetus, 
from  Rowland's  discovery  of  the  concave  grating  in  1881. 
By  its  use  measurements  have  attained  a  degree  of  accuracy 
otherwise  unapproachable,  and  whilst  this  is  specially  true  of 
the  values  obtained  by  the  coincidence  method,  it  also  applies, 
to  wave-lengths  directly  determined ;  it  is  the  only  instru- 
ment which  is  available  for  use  with  all  rays,  including  the 
ultra-violet  and  the  infra-red,  and,  as  no  lens  is  necessary 
between  the  slit  and  eyepiece,  defects  from  loss  of  light  or 
spherical  aberration  are  avoided ;  the  gratings  being  astig- 


34  SPECTRUM  ANALYSIS. 

matic  a  luminous  point,  such  as  a  spark,  appears  in  the  field 
of  view  as  a  line,  thus  greatly  facilitating  the  comparison  of 
solar  lines  with  those  of  metals,  and  the  enlargement  of 
spectra.  Photographs,  both  of  the  visible  and  invisible  por- 
tions of  the  spectrum,  are  easily  obtained,  and  their  accuracy 
is  necessarily  far  in  excess  of  the  drawings  prepared  from 
ocular  observation ;  as  it  is  generally  used  in  conjunction  with 
a  camera,  its  detailed  description  is  reserved  for  the  following 
chapter.  When  employed  for  ocular  purposes,  the  camera  is 
replaced  by  a  cross-wires  and  micrometer;  with  a  highly 
accurate  screw  of  125  mm.  the  measuring  arrangement  resem- 
bles a  dividing-machine  in  exactitude  rather  than  an  ordinary 
micrometer.  The  use  of  an  eyepiece  with  a  focal  length  of 
-J  inch  gives  results  equalling  those  obtained  with  a  plane 
grating  in  combination  with  a  telescope  enlarging  100-200 
times. 


CHAPTER    IV. 
SPECTROSCOPIC  INSTRUMENTS  FOR  SPECIAL  PURPOSES. 

Spectrometer. — This  instrument  is  employed  when  exact 
measurements  are  required  in  spectrum  analysis,  the  coeffi- 
cient of  refraction  being  determined  by  the  method  of  mini- 
mum dispersion.  The  numerous  instruments  on  the  market, 
whilst  differing  in  detail,  agree  in  principle;  the  one  described 
here  (Fig.  20)  is  constructed  by  Schmidt  and  Haensch  of 
Berlin,  according  to  the  design  of  V.  v.  Lang.  The  stand 
can  be  adjusted  horizontally  by  means  of  levelling-screws;  it 
carries  in  the  middle  a  pillar  with  a  steel  axis;  in  the  centre 
at  the  upper  end  of  this  is  a  metal  plate  with  a  divided  circle, 
at  the  lower  end  a  clamp  and  six  radial  arms  for  the  rotation 
of  the  axis;  fitting  over  the  central  pillar  is  a  stout  bronze 
cylinder  which  carries  the  vernier  circle  at  the  top ;  an 
astronomical  telescope  with  cross-wires  and  counterpoise  is 
fastened  to  the  side,  whilst  the  clamping  arrangement  is 
attached  below.  The  stand  carries  the  micrometer-screws  for 
the  divided  circle  and  vernier,  and  also  the  holder  for  the 
collimator,  which  is  fitted  with  a  lens,  an  adjustable  slit,  and 
a  comparison-prism.  Rising  from  the  central  pillar  through 
the  middle  of  the  divided  circle  is  a  rod  carrying  a  round 
plate,  the  height  of  which  can  be  regulated;  it  also  is  divided, 
has  a  fixed  vernier,  and  serves  to  support  the  prism  or  grating. 
The  circle  is  enclosed  in  a  case  fitted  with  windows,  so  as  to 
protect  it  from  corrosion;  both  it  and  the  outer  vernier-circle 
can  be  rotated  independently;  to  facilitate  readings  the  tele- 

35 


SPECTRUM  ANALYSIS, 


WMMJ  l^-*!>-^   ..*-'•  I 


INSTRUMENTS  FOR   SPECIAL   PURPOSES.  37 

scope  may  also  be  moved  without  altering  the  position  of  the 
circle.  The  instrument  is  provided  with  a 
Gauss'  eyepiece  (Fig.  21),  in  addition  to  one 
of  the  ordinary  form ;  it  has  an  opening  (b)  at 
the  side,  which  admits  light  to  a  plane 
parallel  glass  plate  placed  behind  it  at  an  FlG* 21> 

angle  of  45°  with  the  axis  of  the  telescope;  the  light  is  thus 
reflected  on  to  the  cross-wires.  The  correct  orientation  of 
the  instrument  is  of  considerable  importance.  The  telescope 
is  adjusted  to  infinity  and  placed  at  right  angles  to  the  axis 
of  rotation,  the  cross- wires  and  eyepiece  being  in  sharp  focus; 
the  collimator  must  also  be  adjusted  to  infinity  and  fixed  at 
right  angles  to  the  axis  of  rotation,  whilst  the  refracting  edge 
of  the  prism  is  parallel  with  this. 

The  refractive  index  («)  is  calculated  from  the  angle  of 
refraction  (g)  and  that  of  dispersion  (D).  In  order  to  obtain 
the  former,  the  telescope,  fitted  with  the  Gauss  eyepiece,  is 
adjusted  at  right  angles  to  the  first  prism-face,  and  then 
rotated  until  it. is  at  right  angles  with  the  second  face;  the 
reading  obtained,  subtracted  from  180°,  gives  the  refractive 
angle  (g).  The  angle  of  dispersion  (D)  is  determined  as 
follows:  The  prism  is  removed,  and  the  telescope  with  cross- 
wires  directed  on  the  slit — this  gives  the  zero-point ;  the  prism 
is  then  replaced  in  the  position  of  minimum  dispersion,  and 
the  telescope  again  adjusted  towards  the  slit — the  difference 
in  the  readings  gives  the  angle  of  dispersion  for  the  particular 
color.  The  coefficient  of  refraction  is  then  calculated  by  the 
expression 

sin 


sm 


and  the  wave-length  of  the  refractive  index  n  by  Cauchy's  * 
dispersion-formula 

B        C 

n  =  A  +  -     +      +  .  .  .   ; 


Memoire  sur  la  dispersion  de  la  lumiere  (Prague,  1836). 


30  SPECTRUM  ANALYSIS. 

for  ordinary  purposes  the  last  constants  can  be  neglected,  as 
they  are  very  small.  A  and  B  are  obtained  from  the  expres- 
sions 

B  .    B 

V  A2" 

which  necessitate  the  determination  of  the  refractive  indices 
nl  and  #a  of  the  prism  for  two  rays,  the  wave-lengths  At  and  A2 
of  which  are  accurately  known,  such  as  two  prominent  Fraun- 
hofer  lines. 

Kruss' '  Universal  Spectroscope. — This  instrument  is 
manufactured  by  A.  Kruss  of  Hamburg  from  the  design 
of  G.  Kruss;1  it  is  suitable  for  all  kinds  of  spectro-chemi- 
cal  investigation,  and  admits  of  measurements  being  made 
which  in  accuracy  closely  approach  those  obtained  by  the 
spectrometer.  In  its  general  plan  the  instrument  (Fig.  22) 


FIG.  22. 

resembles  that  of  Bunsen  and  Kirchhoff;  the  telescope  mag- 
nifies seven  times;  the  tube  B  carries  the  scale,  which  is  fixed 
in  the  focus  of  the  objective;  the  100  division  is  adjusted  to 
correspond  with  the  middle  of  the  ZMines;  the  slit  on  the 
collimator  A  is  likewise  sharply  in  the  focus  of  the  objective> 

1  Ber.  19,  2739. 


INSTRUMENTS  FOR   SPECIAL   PURPOSES.  39 

and  parallel  with  the  refracting  edge  of  the  prism.  Two 
different  slits  are  employed,  a  single  one  for  qualitative,  and  a 
double  one  for  quantitative  analysis;  in  the  case  of  the  latter 
both  slits  open  symmetrically  to  the  optical  axis,  so  that  with 
apertures  of  all  sizes  the  spectra  retain  the  medial  position. 
The  single  slit  is  provided  with,  a  detachable  comparison 
prism,  and  its  width  regulated  by  a  micrometer  screw  with  a 
divided  milled  head.  The  halves  5:  and  52  of  the  double  slit 
5  may  be  separately  adjusted  by  means  of  micrometer-screws 
with  the  divided  milled  heads  tl  and  A,.  Two  prisms  are  pro- 
vided, one  of  flint  glass  of  low  dispersive  power  with  an  angle 
of  60°,  and  a  highly  refractive  Rutherf urd  prism ;  they  are 
contained  in  the  case  D,  and  are  retained  in  the  position  of 
minimum  dispersion  by  the  pressure  of  a  spring  under  the 
knob  K.  The  measuring  appliances  are  attached  to  the  tele- 
scope, which,  together  with  its  holder,  may  be  rotated  around 
the  vertical  axis  of  the  instrument  by  a  micrometer  screw 
with  a  milled  head  r^  divided  into  100  parts;  complete  revo- 
lutions of  this  are  read  off  on  a  divided  scale  directly  under 
the  eyepiece.  The  cross-wires  are  moved  independently  by 
a  similar  screw  with  its  milled  head  r2  also  divided  into  100 
parts.  These  arrangements  permit  of  accurate  measurements 
of  spectra;  and  as  the  relationship  of  the  screw-threads  to 
each  other  and  to  the  divisions  of  the  scale  are  known,  the 
measurements  made  by  any  one  can  be  doubly  controlled. 

Spectrophotometer. — A  special  peculiarity  of  the  pre- 
ceding instrument  is  the  double  slit,  first  employed  by 
Vierordt l  in  his  photometric  work  with  absorption-spectra  and 
quantitative  spectrum  analysis.  To  determine  the  quantity 
of  a  colored  substance  in  solution  it  is  poured  into  a  trough 
or  a  Schultz's  glass,  and  placed  in  front  of  one  slit;  the  other 
is  then  closed  until  both  are  of  equal  brightness;  the  move- 


J  P.  A.  140,  172.  Die  Anwendung  des  Spectralapparates  zur  Photo- 
metric der  Absorptionsspectra  und  zur  quantitativen  Analyse  (Tubingen, 
1873). 


40  SPECTRUM  ANALYSIS. 

ment  of  the  slit  is  measured  by  the  divided  screw-head,  the 
amount  of  light  cut  off  being  equal  to  that  absorbed  by  the 
quantity  of  substance  in  solution.  In  Glan's,1  and  Htifner's8 
spectrophotometers  the  diminution  of  the  light  is  not  deter- 
mined by  closing  the  slit,  but  by  polarization. 

Sorby's  Microspectroscope. — It  is  often  desirable  to 
apply  the  spectroscope  to  the  investigation  of  microscopic 
objects,  such  as  rock  sections,  leaves,  the  sap  of  plants, 
opaque  substances,  and  for  the  identification  of  the  coloring 
matter  of  blood  in  medico-legal  cases.  For  this  purpose 
Sorby,3  in  conjunction  with  Browning,  arranged  a  convenient 
combination  of  microscope  and  spectroscope.  The  instrument 
(Fig.  23)  is  inserted  into  the  tube  of  a  microscope  instead  of 
the  ordinary  eyepiece;  the  rays  proceeding  from  the  lens 
pass  successively  through  the  slit,  the  combining  lens,  and  an 
Amici  compound  prism;  at  right  angles  is  placed  a  measuring 
arrangement  consisting  of  a  ray  of  light  from  a  mirror  which 
is  reflected  into  the  eye  of  the  observer  by  the  exterior  face 
of  the  last  prism ;  a  dark  photographed  background  is  pro- 
vided, and  a  delicate  micrometer-screw  which  enables  the  ray 
to  be  accurately  adjusted  to  any  spectrum  or  absorption  line. 
A  second  mirror  serves  to  illuminate  the  comparison-prism, 
and  a  small  stand  at  the  side  on  which  objects  can  be  fixed. 
Light  for  the  mirrors  is  obtained  from  a  single  lamp. 

A  modification  of  this  microspectroscope  devised  by  Abbe 
and  constructed  by  C.  Zeiss  of  Jena  is  shown  in  Fig.  24. 
The  screw  M  fixes  it  in  the  tube  of  the  microscope  in  such  a 
position  that  both  the  mirrors  A  and  O  are  illuminated  by  the 
sun.  The  upper  portion,  containing  the  prisms,  can  be  rotated 
round  the  peg  K  so  as  to  admit  of  the  object  being  adjusted ; 
when  this  is  accomplished  the  prisms  are  turned  until  the 
closing  of  the  catch  L  indicates  that  they  are  in  position. 

1  W.  A.,  i,  351. 

9  J.  pr.  Chem.  [2],  16,  290.     Zeitschr.  f.  phys.  Chem.,  3,  562. 

3  C.  N..  15,  220.     P.  R.  S.,  15,  433. 


INSTRUMENTS   FOR   SPECIAL   PURPOSES.  4! 

The  mirror^4,  indicated  by  dotted  lines,  illuminates  objects 
fastened  to  a  stand  at  the  side ;  the  light  passes  through  an 
opening  to  the  comparison-prism,  which  is  fastened  to  the  slit 


FIG. 


FIG. 


and  is  not  shown  in  the  figure.  A  peculiarity  of  the  instru- 
ment is  found  in  the  measuring  arrangement:  the  scale  N 
gives  the  wave-lengths,  in  parts  of  a  micromillimetre,  of  the 
region  of  the  spectrum,  coincident  with  its  divisions;  the 
compound  prism  is  fixed  between  pieces  of  cork,  and  can  be 
inclined  from  the  vertical  by  means  of  the  spring  Q  and  the 
regulating-screw  P,  so  that  the  divisions  of  the  scale  may  be 
made  to  correspond  exactly  with  the  Fraunhofer  lines;  the 
mirror  O  reflects  the  scale  on  to  the  exterior  prism-face. 

Solar  and  Stellar  Spectroscopes. — The  extensive  appli- 
cation of  spectrum  analysis  to  astronomical  purposes  has 
resulted  in  the  designing  of  a  very  large  number  of  instruments 
suitable  for  such  observations.  Solar  investigations  are  gen- 
erally carried  out  with  fixed  apparatus,  grating  spectroscopes, 


42  SPECTRUM  ANALYSIS. 

spectrometers,  and  angular-vision  spectroscopes  of  high 
dispersive  power,  the  light  being  supplied  by  means  of  a 
heliostat.  The  solar  prominences  could  formerly  only  be 
observed  during  an  eclipse,  but  Lockyer  and  Janssen  simul- 
taneously devised  a  method  by  which  they  may  be  investi- 
gated at  any  time.  For  this  purpose  a  spectroscope  of  high 
dispersive  power  is  required;  it  is  connected  with  a  telescope, 
and  the  slit  of  wide  aperture  directed  tangentially  to  the  solar 
limb.  Any  spectroscope  of  high  dispersive  power  may  be 
employed  for  this  purpose,  if  it  admits  of  rotation  around  the 
collimator-axis  so  as  to  discover  the  prominences.  It  is  not 
easy  to  securely  fasten  a  heavy  spectroscope  to  a  telescope ; 
for  this  purpose  a  special  form  of  stand,  termed  an  adapter, 
has  been  described  by  H.  C.  Vogel,  but  it  is  highly  desirable 
that  the  spectroscope  should  be  as  light  as  possible.  Such  a 


FIG.  25. 

solar  spectroscope,  designed  by  Browning,  is  shown  in  Fig.  25  ; 
an  arrangement  is  provided  by  which  it  can  be  screwed  on  to 
the  eyepiece  of  a  refractor  of  three  or  more  inches  diameter. 
The  screw-ring  carries  a  position-circle,  divided  into  whole 
degrees,  the  pointer  (alidade)  of  which  has  two  adjustable 
bars  at  right  angles;  to  the  front  one  are  attached  the  sup- 
ports for  the  collimator  and  prism-plate.  The  collimator  and 
telescope  are  fixed,  the  five  prisms  move  automatically;  a 


INSTRUMENTS  FOR   SPECIAL   PURPOSES.  43 

reflection-prism  causes  the  rays  to  return  through  the  system, 
so  that  the  effect  of  ten  prisms  is  obtained.  The  measuring 
arrangement  is  on  the  left  of  the  telescope;  it  consists  of  a 
triangular  brass  rod  with  a  micrometer-screw  by  means  of 
which  the  prisms  are  automatically  adjusted  to  the  position 
of  minimum  dispersion  for  the  particular  ray  under  examina- 
tion. The  instrument  shows  six  lines  between  the  two  ZMines 
with  the  sun  at  its  brightest.  Since  the  dispersive  power  can 
be  varied  from  two  to  ten  prisms,  the  instrument  can  also  be 
used  for  stellar  and  other  celestial  observations,  where,  in 
consequence  of  the  feebleness  of  the  light,  a  lower  dispersion 
is  required. 

For  a  general  survey  of  the  sky,  or  for  the  observation  of 
fixed  stars  which  appear  as  points,  a  telescope  may  be  at- 
tached to  a  direct-vision  spectroscope  without  a  slit;  such 
instruments  have  been  designed  by  Zollner,  Secchi,  H.  C. 
Vogel,  McClean,  v.  Konkoly,  and  others,  but  they  are  not 
adapted  for  accurate  measurement. 

For  the  investigation  of  the  spectra  of  meteors,  v.  Konkoly 
recommends  a  direct-vision  spectroscope  with  a  concave 
cylindrical  lens  attached  to  a  small  telescope;  the  field  of 
view  then  includes  about  27°,  and  the  rapid  motion  of  the 
meteorite  is  apparently  diminished. 

Stellar  Spectrometers. — H.  C.  Vogel  has  designed  a 
good  spectrometer  which  is  fastened  to  a  telescope,  and 
permits  of  accurate  stellar  spectroscopic  measurements  being 
made.  More  recently  Adam  Hilger  of  London  has  con- 
structed an  instrument  specially  adapted  for  solar  and  stellar 
work,  and  it  can  also  be  mounted  on  a  stand  for  use  in  the 
laboratory. 

Spectrographs. — The  use  of  a  combination  of  spectro- 
scope and  photographic  camera,  termed  a  spectrograph,  has 
led  to  extremely  valuable  results:  errors  of  observation  and 
drawing  are  avoided;  records  are  obtained  of  the  invisible 
infra-red  and  ultra-violet  regions,  and  also  of  celestial  objects, 


44  SPECTRUM  ANALYSIS. 

the  light  from  which  is  too  feeble  to  affect  the  eye,  and 
necessitates  a  prolonged  exposure.  H.  W.  Vogel1  has 
designed  a  large  and  a  small  form  of  this  instrument;  the 
latter  has  a  wedge-shaped  slit,  a  collimator-lens,  an  Amici 
prism  of  five  members,  and  an  aplanatic  lens  which  throws  the 
image  on  the  ground-glass  or  sensitized  plate  at  the  back  of 
the  camera.  The  larger  instrument  is  adapted  for  deflected 
rays,  has  two  prisms  of  60°,  and  is  rotatable  around  both  the 
vertical  and  horizontal  axes,  which  permits  it  to  be  used,  for 
solar  and  terrestrial  purposes.  Ostwald  a  has  suggested  the 
following  procedure  for  the  photography  of  absorption-spectra : 
A  horizontal  plate  is  screwed  on  to  the  objective  of  a  photo- 
graphic camera,  to  which  a  spectrometer-prism  and  collimator- 
tube  containing  the  lens  are  attached ;  the  spectrum  is  thrown 
on  the  ground-glass  plate  by  a  Luter's  aplanatic  lens  of 
40  cm.  focal  length,  and  brought  to  accurate  focus  by  obser- 
vation of  the  solar  lines.  The  prism  employed  has  a  refracting 
angle  of  60°,  and  is  filled  with  ^-bromonaphthalene;3  its  dis- 
persive power  is  especially  high  in  the  ultra-violet.  An  Auer 
incandescent  gas-lamp  is  recommended  as  the  source  of  light. 
Photographs  of  stellar  spectra  are  obtained  by  attaching 
the  spectrograph  directly  to  a  telescope.  The  large  spectro- 
graph at  the  Astrophysical  Institute  at  Potsdam  4  is  an  exam- 
ple of  such  an  instrument;  it  gives  extremely  accurate 
reproductions  of  stellar  spectra.  The  ocular  of  an  eleven-inch 
refractor  is  removed,  and  a  strong  stand  attached  in  its  place; 
to  one  end  the  spectrograph  is  screwed;  the  cbllimator-tube 
of  this,  in  order  to  insure  stability,  is  sustained  on  a  conical 
steel  holder  with  an  adjusting  arrangement  and  a  scale.  Next 
to  the  collimator  is  a  stout  circular  holder  for  the  two  Ruther- 
fiird  prisms  of  high  dispersive  power;  beyond  this  is  a  conical 

1  P.  A.  154,  306;  156,  319. 

2  Zeitschr.  f.  phys.  Chem.  9,  579. 

3  Walter,  W.  A.  42,  511. 

4  Scheiner,  Spectralanal.  der  Gestirne  (Leipzig,  1890),  p.  109. 


INSTRUMENTS  FOR   SPECIAL   PURPOSES. 


45 


camera  which,  to  guard  against  vibration,  is  attached  by  stays 
to  the  far  end  of  the  collimator-tube.  The  collimator  and 
object  lenses  are  achromatic  to  chemically  active  rays.  About 
40  cm.  from  the  slit,  in  the  focus  of  the  refractor  objective,  is 
placed  a  Geissler's  tube  containing  hydrogen ;  this  serves  to 
illuminate  the  slit,  and  also  affords  a  means  of  measuring  the 
displacement  of  the  lines  caused  by  the  motion  of  the  star 
across  the  field  of  view,  since  the  photograph  shows  the  stellar 
spectrum  together  with  the  //^-lines.  The  refractor  is  set  in 
motion  so  as  to  maintain  the  middle  of  the  slit  exactly  on  the 
star.  Bromo-silver  gelatine  plates  are  usually  employed. 

Rowland's  Concave-grating  Spectrograph.1 — The  merits 
of  this  instrument   have  been   enumerated   in  the  preceding 


FIG.  26. 


chapter;  its  separate  parts  require  special  arrangement,  for, 
as  Rowland  has  pointed  out  in  his  theory  of  the  concave 
grating,  normal  spectra  are  only  obtained  if  the  slit,  grating, 
and  camera,  or  eyepiece,  are  placed  in  the  periphery  of  a 


1  P.  M.  [5]  16,  197.  Astronomy  and  Astrophysics  (1893),  12,  129. 
Johns  Hopkins  University  Circulars  (1889),  8,  No.  73,  P-  73-  Ames,  ibid., 
8,  No.  73,  p.  69.  P.  M.  (1889)  [5]  27. 


46 


SPECTRUM  ANALYSIS. 


circle  of  which  the  grating  forms  a  segment;  the  diameter  of 
the  circle  is  dependent  on  the  concavity  of  the  grating.  This 
adjustment  is  effected  mechanically  by  means  of  two  rods  at 
right  angles;  the  grating  is  placed  at  their  point  of  intersec- 
tion, so  that  it  is  always  maintained  at  a  constant  distance 
from  the  camera.  The  external  appearance  of  the  instrument 
is  shown  in  Fig.  26.  Fig.  27  exhibits  the  plan  of  the  one 


FIG.  27. 


employed  by  Rowland  for  his  classical  measurements  of  the 
solar  lines.  It  consists  of  two  stout  wooden  beams  AB  and 
15  X  33  cm.  and  7  metres  in  length;  one  is  fixed,  but 


INSTRUMENTS  FOR   SPECIAL   PURPOSES. 


47 


the  other  is  slightly  movable,  by  means  of  screws,  about  the 
point  A.  The  beams  are  provided  with  rails  for  the  wheels  at 
each  end  of  the  carriages  D  and  E  \  apertures  are  cut  in  these  ex- 
actly coincident  with  the  rail  to  receive  the  peg  of  the  trans- 
verse beam  FG,  which  is  made  of  4-inch  wrought-iron  tube; 
its  length  corresponds  with  the  concavity  of  the  grating,  and, 
in  the  case  of  a  six-inch  grating  with  1 10,000  lines,  is  about 
6.55  metres,  with  15  cm.  for  adjustment.  The  grating  is  fixed 


FIG.  28. 

to  D,  and  the  camera  to  E\  the  latter  is  shown  in  Fig.  28. 
It  consists  of  the  fixed  box  B,  and  the  movable  case  A  to  hold 
the  photographic  plate,  which  is  bent  to  the  desired  form  by 
pressure  against  a  rubber  pad;  the  wooden  rod  C  carries  a 
brass  plate  with  a  long  narrow  opening;  it  is  rotatable  about 
its  horizontal  axis,  and  is  used  to  obtain  a  comparison-photo- 
graph. The  sensitive  plates  are  48  X  5  cm.,  and  1.8  mm.  in 
thickness;  the  breadth  of  the  spectrum  varies  according  to  the 
order,  from  6  mm.  to  10  cm.  The  grating-holder  is  shown 
in  Fig.  29,  and  consists  of  a  massive  bed-plated,  and  a  mov- 
able perpendicular  frame  B\  to  this  a  brass  rod  D  is  fastened 
by  the  screw  P,  and  is  movable  about  this  axis  by  the 


SPECTRUM  ANALYSIS. 


screw  5;  a.second  movable  frame  is  attached  to  the  brass  rod 
by  means  of  the  screw  P,  and  is  rotatable  about  P'  by  the 


) 

p 

p 

b 

1  3  ' 

FIG.  29 

FIG.  30. 

screw  S';  it  carries  the  grating,  supported  on  two  projec- 
tions, and  fixed  by  wax  so  as  to  be  quite  free  from  pressure, 
The  orientating-screws  work  against  springs  so  that  the  grat- 
ing is  readily  movable  in  any  direction.  Gratings  of  varying 
diameter  are  used  with  10,000  to  20,000  lines  to  the  inch;  for 
most  purposes  the  first  is  sufficient,  but  the  last  is  preferable 
for  work  with  the  ultra-violet  rays.  The  slit  (Fig.  30)  must 
be  capable  of  being  raised,  lowered,  and  rotated  about  its 
horizontal  axis;  the  latter  is  of  special  importance,  as  a  sharp 
image  can  only  be  obtained  if  the  slit  and  lines  are  exactly 
parallel.  The  aperture  is  regulated  by  means  of  a  micrometer- 
screw;  as  a*rule  its  width  is  only  0.025  mm-  The  light  from 
the  electric  spark  or  arc,  or  from  a  heliostat  if  the  solar  spec- 
trum is  being  examined,  is  directed  on  a  convergent  quartz 
lens  in  the  focus  of  the  slit,  whence  it  passes  directly  to  the 
slit;  if  the  source  of  light  is  at  the  side,  a  reflecting  prism  is 
employed.  The  astigmatism  of  the  grating  precludes  the 
simultaneous  photographing  of  a  spectrum  and  a  superposed 
comparison-spectrum,  as  with  the  prism-spectroscope;  the 
comparison-photographs  are  therefore  made  separately,  but  on 
the  same  plate.  By  means  of  the  arrangement  at  the  back 


INSTRUMENTS  FOR   SPECIAL   PURPOSES. 


49s 


of  the  camera,  the  comparison-spectrum  is  received  in  the 
middle  of  the  plate,  and  the  spectrum  under  examination; 
above  and  below.  A  triangular  stand  placed  between  the  slit 
and  the  quartz  lens  serves  to  support  vessels  containing 
absorbent  solutions  to  cut  off  the  spectra  of  other  orders 
which  would  otherwise  obscure  the  one  employed. 

These  concave-grating  spectroscopes,  of  excellent  finish,, 
are  manufactured  by  John  A.  Brashear  of  Allegheny. 

By  means  of  Rowland's  coincidence  method  a  knowledge 
of  one  absolute  wave-length  enables  ah  others  to  be  deter- 
mined, relatively  to  this,  with  an  extremely  high  degree  of 
accuracy.1  Taking  Dl  as  the  basis,  it  is  photographed  in  the 
spectra  of  as  many  orders  as  the  grating  permits;  the  other 
orders  are  thus  obtained  simultaneously  on  the  same  plate, 
viz.,  Dl  in  the  first  order,  2948  in  the  second,  and  1965  in  the 
third;  with  Dl  in  the  second  order,  3931  in  the  third,  2948  in 
the  fourth,  2358  in  the  fifth,  etc.  The  following  table  gives 
the  coincidences  with  £>l  in  the  first  nine  orders: 


I 

5896 

2 

2948 

5896 

3 

I965 

393i 

5896 

4 

2948 

4422 

5896 

5 

2358 

3538 

4717 

5896 

6 

1965 

2948   3931 

49T3 

5896 

7 

2527 

3369 

4211 

5054 

8 

2211 

2948 

3685 

4422 

9 

2620 

3275 

3931 

i 

The  distance  between  the  Z>,-line  and  separate  lines  of 
these  different  orders  is  measured,  and  the  wave-lengths 
approximately  calculated  from  the  grating  constant,  which  is 
known  with  i  fair  degree  of  accuracy,  and  its  concavity;  if  the 
wave-length  of  the  lines  does  not  differ  by  more  than  50 

1  Comp.  Kayser,  A.  B.  A.  1890. 


50  SPECTRUM  ANALYSIS. 

Angstroms  from  that  of  Z>,,  a  result  is  immediately  obtained, 
correct  within  0.5  of  an  Angstrom.  The  accuracy  of  this 
result  may  be  increased  to  any  desired  degree;  if,  for  exam- 
ple, the  wave-lengths  4422  and  47 17  ±0.5  are  photographed 
on  a  plate,  and  their  distance  measured,  the  result  is  accurate 
to  one  third  per  cent,  since  their  difference  of  300  units  is 
known  to  be  exact  to  one  unit;  with  this  higher  approxima- 
tion the  calculation  is  repeated,  giving  data  of  still  greater 
accuracy,  and  so  on. 

Rowland   obtained    his   system    of   wave-lengths    in    this 
manner;  between  A  2400  and  A  7000  it  is  exact  within  at  least 

o 

o.oi  Angstrom,  and,  together  with  his  atlas  of  the  solar 
spectrum,  it  forms  the  basis  of  all  spectroscopic  measure- 
ments. 


CHAPTER   V. 
SPECTROSCOPIC   ADJUNCTS. 

Flame-spectra. — The  flame  of  a  Bunsen  burner  is  suffi- 
cient to  volatilize  compounds  of  the  metals  of  the  alkalis  and 
alkaline  earths;  for  compounds  of  these  metals  which  are  par- 
ticularly difficult  to  vaporize  a  Terquem  burner  may  be  used, 
as  recommended  by  Wiedemann  and  Ebert.  The  flame, 
spectra  of  many  substances  can  only  be  obtained  by  the  use 


of  a  blowpipe,  hydrogen,  or  oxyhydrogen  flame,  all  of  which 
were  employed  by  Kirchhoff  and  Bunsen.  A  Barthel  or 
other  suitable  spirit-lamp  may  take  the  place  of  a  gas-burner 
if  necessary.  In  many  cases  a  relatively  cool  flame  is  desir- 
able; this  can  be  obtained,  according  to  Salet's  suggestion, 
by  placing  the  gas-flame  in  contact  with  a  plate  of  marble  or 
metal,  the  opposite  side  of  which  is  kept  cool  by  means  of  a 


52  SPECTRUM  ANALYSIS. 

stream  of  water.  The  substance  is  brought  into  the  flame  on 
a  pbtinum  wire;  one  end  is  bent  to  a  -loop,  and  the  other 
is  fused  into  a  small  piece  of  glass  tubing  which  is  fastened 
to  the  arm  of  a  Bunsen  stand  (Fig.  31).  IVIitscherlich's  appa- 
ratus is  employed  when  a  flame-spectrum  is  required  during 
a  considerable  period  of  time.  It  consists  of  a  series  of  glass 


tubes  (Fig.  32)  closed  at  the  upper  end ;  the  lower  end  is  bent, 
and  filled  with  a  bundle  of  slender  platinum  wires  or  threads 
of  asbestos  c\  the  substance  under  examination  is  dissolved, 
a  little  hydrochloric  acid  or  ammonium  acetate  added,  to  pre- 
vent the  formation  of  crusts  on  the  wires,  and  the  solution 
placed  in  the  tubes.  Gouy's1  method  consists  in  causing  the 
air  or  gas,  before  it  reaches  the  burner,  to  pass  through  a 
vessel  containing  the  substance  in  solution  or  in  a  very  finely 
divided  state.  Neither  of  these  arrangements  is  satisfactory 
when  a  uniformly  bright  flame  has  to  be  maintained  during 

1  A.  c.  p.  [5]  18,  25.  The  construction  of  the  pulverizing  apparatus  is 
described  in  Ebert's  work  Anleitung  zum  Gasblasen  (Leipzig,  1895,  2d  ed.)» 
P-  59- 


SPECTROSCOP1C  ADJUNCTS. 


53 


several  hours;  for  such  purposes  Eder  and  Valenta's1  appa- 
ratus (Fig,  33)  can  be  employed.  It  consists  of  a  heavy 
metal  pedestal  P,  rotatable  about  its  vertical  axis;  the  Bunsen 
or  Terquem  burner  #  is  fitted  with  a  platinum  ring;  the  wheel 
s  is  adjustable,  and  inclined  at  an  angle  of  45°:  it  consists  of 
two  nickel  plates  carrying  a  circle  of  platinum  gauze  n,  which 
projects  2-3  cm.  beyond  the  circumference  of  the  wheel,  and 


FIG.  33. 

dips  into  the  vessel  £•  containing  the  solution  of  the  substance. 
The  axle  a,  connected  with  the  cone  c,  permits  of  the  rota- 
tion of  the  wheel  by  clockwork  or  some  suitable  motor. 
Mitscherlich,*  Wolf  and  Diacon,3  and  Salet  *  place  readily 
volatilizable  substances  in  a  glass  tube  fused  to  the  hydrogen 
generator,  and  heat  them  in  the  gas  which  is  then  burnt  at  a 
platinum  jet  fused  to  the  other  end  of  the  tube.  For  pro- 


1  Denkschr.   der   mathem.-naturw.    Classe   der  Wien.    Akad.  (1893)  60, 
468. 

2  P.  A.  (1863)  121. 

8  Mem.  de  1'Acad.,  Montpellier,  1863. 

4  A.  c.  p.  (1873)  [4]  28.      Spectroscopie  (Paris,  1888). 


54  SPECTRUM  ANALYSIS. 

longed  observations  on  haloid  componnds  of  metals,  the  coal- 
gas  must  be  mixed  with  chlorine,  bromine,  or  iodine  vapor. 

The  Bunsen  burner  gives  a  temperature  of  about  2300°, 
and  none  of  the  others  are  hot  enough  to  show  more  than  a 
comparatively  small  number  of  spectra;  the  electric  arc  and 
spark  are  of  much  wider  application. 

The  Electric  Arc. — The  temperature  of  the  arc  ranges 
from  3OOO°-35OOC  (Violle),  and  is  the  most  generally  appli- 
cable of  all  methods  of  producing  metallic  spectra,  as  its  high 
luminosity  permits  the  use  of  gratings,  and  also  renders  it 
suitable  for  projection.  Kayser  and  Runge  employed  it  in 
their  accurate  measurements  of  the  spectra  of  terrestrial  sub- 
stances; usually  they  used  a  current  of  50  volts  and  20-30 
amperes,  but  occasionally,  for  the  shorter  wave-lengths,  40 
amperes  were  required.  The  anode  carbon  is  placed  below, 
as  it  burns  to  a  cavity  which  serves  to  receive  the  substance, 
and  its  temperature  is  higher  than  the  cathode.  In  order  to 
prevent  the  metal  or  salt  from  overflowing  the  cup,  rods  of 
not  less  than  2  sq.  cm.  are  employed.  The  formation  of 
oxide  may  be  prevented  by  boring  the  upper  carbon,  and 
conducting  a  current  of  some  gas  through  it,  or,  better,  by  the 
use  of  a  block  of  gas-carbon,  quicklime,  marble,  or  magnesia 
as  suggested  by  Liveing  and  Dewar.1  The  block  is  pierced 
completely  through  in  two  horizontal  directions  crossing  at 
right  angles  in  the  middle;  glass  tubes  carrying  the  carbon 
rods  are  fitted  to  two  opposite  openings;  light  is  emitted  by 
the  third,  and  the  fourth  serves  for  the  admission  of  gas 
(carbon  dioxide  or  hydrogen);  a  fifth  opening,  immediately 
above  the  point  of  intersection  of  the  others,  is  for  the  intro- 
duction of  the  substance.  The  arc  plays  on  the  body  under 
examination  and  volatilizes  it;  Kayser  and  Runge  recommend 
the  use  of  a  magnet  to  cause  the  arc  to  impinge  directly  on 
the  substance  below  the  opening.  The  apparatus  is  also 

1  P.  R.  S.  (1879).     Proc.   Cambridge  Phil.   Soc.   (1882)  4.       Kayser  and 
Runge,  A.  B.  A.  1890,   1891. 


*  SPECTROSCOPIC  ADJUNCTS.  5S 

useful  for  observing  the  reversal  of  the  lines  by  absorption,  as 
the  opening  through  which  the  light  passes  is  always  full  of 
comparatively  cool  vapor;  the  intensity  of  the  lines  is  less 
with  the  block  than  when  the  substance  is  volatilized  directly 
from  the  carbon  rod.  A  series  of  carbon  bands  are  almost 
always  observed  above  the  metallic  spectrum  when  metals  or 
salts  are  volatilized  between  carbon  terminals;  this  often  adds 
greatly  to  the  difficulty  of  measuring  the  lines,  and,  in  order 
to  avoid  error,  an  exact  knowledge  of  these  bands  is  necessary. 
The  difficulty  may  be  obviated  by  using  terminals  of  the  par- 
ticular metal  under  observation,  but  this  has  other  drawbacks: 
the  lamp  is  no  longer  automatically  regulated,  as  the  glowing 
rods  of  metal  fuse  immediately  they  come  into  contact,  whilst, 
if  the  arc  is  extinguished  for  a  moment,  the  terminals  become 
coated  with  oxide,  which  is  a  bad  conductor,  and  requires  to 
be  scraped  off. 

The  Electric  Spark. — The  spark  from  an  influence 
machine  or  induction-coil  may  also  be  used  for  the  production 
of  luminous  vapor;  the  spectra  of  gases  are  produced  solely 
by  its  help,  it  is  more  convenient  than  the  arc,  and  is  there- 
fore employed  more  frequently,  although  spark-spectra  exceed 
those  of  the  arc  in  complexity,  and  their  nature  is  not  at  all 
clearly  understood.  The  temperature  of  the  spark  varies 
between  wide  limits;  E,  Wiedemann  1  observed  a  temperature 
of  87,000°  in  a  Geissler  tube. 

The  induction-spark  differs  with  the  construction  of  the 
coil;  if  this  is  composed  of  a  large  number  of  turns  of  thin 
wire,  a  high  potential  is  obtained,  whilst  with  shorter  and 
thicker  wire  the  potential  is  reduced,  and  the  quantity  of 
electricity  increased.  The  intensity  of  the  discharge  may  be 
heightened  by  the  use  of  more  powerful  primary  batteries,  by 
the  introduction  into  the  circuit  of  one  or  more  Leyden  jars, 
or  by  increasing  the  length  of  the  spark-gap.  It  is  usual  to 

1  W.  A.  (1879)  6,  298. 


5°  SPECTRUM  ANALYSIS. 

connect  the  poles  with  a  condenser  as  shown  in  Fig.  34. 
The  wire  K'p'  connects  the  outer  coating  of  the  jar  L  with 
one  pole  of  the  coil,  whilst  the  other  is  joined  with  the  spike 
T,  whence  the  sparks  pass  to  the  plate  P  connected  with  the 
inner  coating  of  the  jar.  The  wires  MK,  M ' Kr  lead  to  the 
stand  H,  to  which  the  metallic  electrodes  EE'  are  fastened, 


FIG.  34. 

and  the  spark  is  produced  between  them.  The  intensity  and 
quantity  of  the  current  can  also  be  increased  when  an  influ- 
ence machine  is  used;  the  poles  are  connected  in  a  similar 
manner  with  a  Leyden  jar,  and  the  potential  may  be  raised 
by  prolonging  the  path  of  the  spark. 

The  simplest  means  of  obtaining  the  line-spectrum  of  a 
-metal  is  to  pass  the  spark  between  electrodes  composed  of  it; 
particles  are  then  detached  and  volatilized.  The  spectrum 


SPECTROSCOPIC  ADJUNCTS. 


57 


of  the  atmosphere,  consisting  of  the  nitrogen,  oxygen,  and 
hydrogen  lines,  always  accompanies  that  of  the  metal  (comp. 
nitrogen,  Chapter  VII).  In  cases  where  a  metal  is  not  avail- 
able, a  solution  of  one  of  its  salts  may  be  used;  this  is  made 
the  cathode  and  the  spark  passed  over  it.  Delachanal  and 
Mermet's  l  apparatus  is  very  convenient  for  use  in  this  con- 
nection, as  it  permits  the  observation  of  the  spectra  during  a 
considerable  period.  It  consists  of  a  glass  vessel  (A,  Fig.  35), 
15  mm.  in  diameter,  with  a  platinum  wire  fused  through  the 
lower  end,  and  connected  with  the  cathode 
of  the  coil;  over  it  is  placed  a  conical 
capillary  tube  D  projecting  5  mm.  above 
the  end.  The  upper  part  of  the  vessel  is 
closed  with  a  cork  C,  through  which  is 
passed  a  glass  tube  B  with  a  platinum  wire 
fused  to  it;  the  end  d  projects  and  forms 
the  anode.  The  salt  solution  is  added  up 
to  half  the  height  of  the  cathode ; 
it  rises  by  capillarity  to  the  end 
of  D,  and  each  spark  volatilizes 
a  small  portion.  No  loss  of  sub- 
stance occurs,  the  slit  of  the 
spectroscope  is  protected  from 
splashing,  and  the  sparks  are 
uniform,  but  they  almost  always 
attack  the  glass,  causing  the  pro- 
duction of  foreign  spectra,  such 
as  those  of  calcium,  lead,  etc. 
Hartley's2  apparatus  (Fig.  36)  is 
free  from  this  drawback;  the  ^3* 

solution  is  poured  into  a  U  tube  to  one  limb  of  which  a 
graphite  electrode  is  fitted,  the  surface  having  a  number  of 
deep  grooves  cut  to  facilitate  the  ascent  of  the  liquid.  The 

1  C.  r.  (1875)  81.     Journ.  de  Phys.  de  d'Almeida  (1876),  5,  10. 
*  P.  T.  (1884)  175,  49.  325- 


5  SPECTRUM  ANALYSIS. 

upper  electrode  may  be  either  of  metal  or  graphite,  preferably 
the  latter;  both  are  chisel-shaped,  connected  with  the  coil  by 
means  of  platinum  wires,  and  placed  exactly  above  one 
another  and  in  a  line  with  the  slit.  Other  forms  of  apparatus 
designed  for  the  same  purpose  have  been  described  by 
Bunsen,1  H.  W.  Vogel,2  Lecoq  de  Boisbaudran,3  Salet,4  and 
Dupre/ 

Geissler's  or  Pliicker's  Tubes. — Plucker's  method "  is 
used  for  the  investigation  of  gases;  it  consists  in  passing  an 
electric  discharge  through  rarefied  gas  contained  in  a  Geissler 
tube  (Fig.  37).  The  middle  of  the  tube  is  usually  a  capillary; 


FIG.  37. 

platinum  wires  are  fused  through  the  wide  closed  ends,  and 
connected  inside  with  aluminium  wires,  as  the  passage  of  the 
current  detaches  particles  of  platinum  which  are  gradually 
deposited  on  the  glass;  the  light  is  more  concentrated  in  the 
capillary,  which  becomes  luminous,  and  is  therefore  placed  in 
front  of  the  slit.  The  tubes  are  rilled  by  means  of  side  tubes 
at  each  of  the  wide  portions;  one  is  connected  with  a  mercury- 
pump,  and  the  gas  introduced  through  the  other.  When  the 
operation  is  completed  the  side  tubes  are  sealed  off;  this  is 
often  attended  with  difficulty  on  account  of  the  entrance  of 
air  due  to  the  low  pressure,  1-2  mm.,  which  is  necessary  in 
order  to  secure  the  maximum  degree  of  brightness.  Tubes 
intended  for  observation  during  several  hours  may  be  closed 


1  P.  A.  155,  230. 

2  Prakt.  Spectralanalyse  (Berlin,  1889). 

3  Spectres  lumineux  (Paris,  1874). 

4  Spectroscopie  (Paris,  1888). 

5  La  nature,  1882,  220. 

6  P.  A.  (1859)  107,  497- 


SPECTROSCOPIC  ADJUNCTS.  59 

by  means  of  stoppers  accurately  ground  and  lubricated.1 
Cornu  2  and  Deslandes 3  have  given  special  instructions  for  the 
filling  of  Geissler  tubes.  Air  is  not  the  only  impurity  which 
is  liable  to  be  met  with  under  extremely  low  pressures;  the 
bands  of  carbon  monoxide  are  frequently  observed,  and  this 
is  very  difficult  to  remove.  Hasselberg1  considers  that  it  is 
only  occasionally  derived  from  the  fat  and  rubber  at  the  joints ; 
it  is  probably  liberated,  together  with  carbon  dioxide  and 
other  substances,  from  the  glass  by  the  electric  discharge. 
Another  disadvantage  of  these  tubes  is  the  thick,  irregular, 
and  non-homogeneous  nature  of  the  wall  of  the  capillary 
which  causes  it  to  act  as  a  cylindrical  lens,  and  sometimes 
produces  displacement  of  the  spectrum  lines.  To  correct 
this  Monckhoven,4  Piazzi-Smyth,5  Salet,6  Hasselberg,7  and 
others  have  constructed  tubes  with  the  capillary  at  right 
angles  to  the  wide  parts  so  that  it  is  observed  "end  on." 
In  order  to  obviate  difficulties  arising  from  the  use  of  elec- 
trodes Salet "  has  prepared  tubes  without  them ;  instead  the 
wide  portions  are  covered  with  tin-foil,  or,  if  the  tempera- 
ture is  too  high,  with  gold  leaf;  the  tubes  are  connected  with 
an  induction-coil  or  with  a  Holtz  machine,  and  the  discharge 
takes  place  through  influence;  but  under  these  circumstances 
the  temperature  in  the  tube  is  much  lower  than  when  the 
current  is  directly  transmitted. 

Other  difficulties  attend  the  use  of  Geissler  tubes:  the 
observed  phenomena  may  be  produced  by  minute  traces  of 
foreign  bodies,  and  not  by  the  gas  itself;  absorption  by  the 
glass  and  electrodes,  and  the  extremely  high  temperature 

1  Hasselberg,  Mem.  de  1'Acad.  de  St.  Petersb.  (1883)  [7]  31,  No.  14. 

2  J.  d.  phys.  de  d'Almeida  (1886)  [2]  5,  100. 
A.  c.  p.  (1888)  [6]  15,  28. 

Les  Mondes,  1877. 

N.  19,400,  458;  20,  75. 

A.  c.  p.  [4]  38,  52. 

Mem.  de  1'Acad.  de  St.  Petersb.  (1882)  [7]  30,  No.  7. 

C.  r.  73,  559. 


60  SPECTRUM  ANALYSIS. 

attainable,  also  influence  the  result,  but  these  causes  are 
insufficient  to  explain  many  puzzling  phenomena.  Liveing 
and  Dewar,  and  also  Ames,  have  suggested  that  these  are  due 
to  the  discharge  producing  special  wave-motions  of  the  atoms, 
and  not  the  pure  spectrum  of  the  substance  under  examina- 
tion, whilst  others  believe  that,  under  its  influence,  the 
molecules  undergo  electrolytic  dissociation  and  the  atoms  are 
set  in  violent  motion;  it  is  at  present  impossible  to  give  a 
satisfactory  explanation  of  the  matter. 

Observation  of  the  Invisible  Regions  of  the  Spectrum. 
— Only  the  small  portion  of  the  spectrum  between  wave- 
lengths 400^^  and  760^^  is,  in  ordinary  circumstances,  visible 
to  the  eye,  but  the  part  beyond  8oo///f  becomes  perceptible 
if  the  shorter  waves  are  cut  off  by  means  of  dark-red  glass, 
whilst  those  far  beyond  400/7^  are  seen  if  the  longer  waves 
are  eliminated.  The  region  beyond  76o/*/*  is  termed  the 
infra-red,  whilst  that  below  4OO////  forms  the  ultra-violet; 
in  the  former  Langley  1  reached  a  wave-length  of  5300^,  and 
Rubens2  one  of  5/50^/1.  In  the  ultra-violet  Schumann,3 
using  gelatine  plates,  obtained  photographs  of  a  group  of  lines 
of  A  i62/^,  and  hydrogen  lines  of  about  ioo////.  Soret 4  has 
devised  a  method  of  rendering  the  ULTRA-VIOLET  visible  by 
employing  the  fluorescence  produced  by  the  waves  of  short 
length;  it  consists  in  the  introduction  of  a  fluorescent  object, 
such  as  a  plate  of  uranium  glass,  into  the  eyepiece  of  a  prism 
spectroscope.  H.  v.  Helmholtz  5  accomplished  the  same  pur- 
pose by  placing  a  thin  film  of  quinine  sulphate  in  the  telescope 
at  the  spot  where  the  objective  forms  a  true  image  of  the  spec- 
trum. Special  instruments,  with  lenses  and  prisms  of  quartz, 
are  required  for  the  investigation  of  the  ultra-violet  rays,  as 

1  W.  A.  (1884)  22,  598.     A.  c.  p.  (1886)  [6]  9,  433. 

2  W.  A.  (1892)  45,  238. 

3  Wien.  Ber.  1892.     Photogr.  Rundschau,  1890,  1892. 

4  Arch.  sc.  phys.  et  nat.  (1877)  [2]  57,  319;   61.  322;    63,  89;    [3]  4,   261; 
9,  513;  10,  429.     A.  c.  p.  (1877)  [5]  11.     C.  r.  (1878)  86,  1062;  97,  314,  572. 

6  Optique  physiologique,  p.  352. 


SPECTROSCOPIC  ADJUNCTS.  6 1 

they  are  absorbed  by  glass;  those  of  35OyUyw  to  a  considerable 
extent,  and  those  of  about  SOO^yw  completely.  Stokes1 
recommends  quartz  for  this  kind  of  work,  but  Schumann* 
found  that  it  absorbs  the  rays  below  2OO//yu,  and  was  obliged 
to  substitute  it  by  fluor-spar;  his  observations  on  waves  of 
shortest  length,  referred  to  above,  were  made  with  such 
apparatus,  the  spectrograph  being  rendered  vacuous.  Grating 
spectroscopes  are  specially  well  adapted  for  work  with  the 
ultra-violet  if  the  use  of  glass  is  avoided;  these  rays  are  also 
absorbed  by  the  atmosphere,  which  accounts  for  the  sudden 
extinction  of  the  solar  spectrum  at  300/^5  this  is  extended, 
Cornu  *  found,  with  the  sun  at  its  zenith. 

Photography  has  latterly  superseded  all  other  methods  of 
investigating  the  ultra-violet  rays;  those  below  200/^/1  are 
absorbed  by  gelatine,  and  for  such  rays  Schumann''  employed 
plates  without  a  gelatine  film. 

The  INFRA-RED  rays  may  be  detected  by  their  thermal  and 
photochemical  properties,  and  by  means  of  phosphorescence. 
Their  existence  was  first  shown  by  William  Herschel*  in  1800. 
During  an  investigation  of  the  heating  power  of  various  regions 
of  the  spectrum  he  found  that  the  thermometer  was  most 
affected  beyond  the  visible  red.  The  thermal  effect  was 
shown  by  Melloni 6  to  be  influenced  by  the  nature  of  the 
prism,  rock  salt  being  extremely  readily  transparent  to  long 
waves;  later  it  was  discovered  that  fluor-spar  and  sylvine  are 
equally  suitable,  and  the  thermopile  was  used  instead  of  a 
thermometer.6  With  a  grating  spectroscope  all  absorption 
by  the  prism  is  avoided,  but  the  distribution  of  the  heat  is 
different,  the  maximum  being  in  the  yellow.  In  place  of  a 

1  P.  T.  1852,  p    463. 

2  Phot,  Rundschau,  1890. 
5  C.  r.  (1879)  88. 

4  P.  T.  (1800)  90. 

5  A.  c.  p.  (1833)  [2]  55. 

6  Franz,  P.  A.   (1855)  94.     J.  Miiller,  ibid.  (1858)  105.     Lamansky,  ibid. 
(1872)  146.     Mouton,  C.  r.  (1879)  88;  89.     Desains,  ibid.  (1880)  90;  (1882)  94. 


62  SPECTRUM  ANALYSIS. 

thermopile,  Langley's  '  actinic  balance  or  bolometer  is  em- 
ployed;  by  its  means  a  rise  in  temperature  of  0.000001°  C. 
may  be  detected.  It  consists  of  a  Wheatstone  bridge,  the 
arms  being  formed  of  two  extremely  thin  blackened  wires  of 
equal  resistance;  if  the  temperature  of  one  changes,  the 
equilibrium  is  disturbed  and  the  galvanometer  affected. 
With  the  aid  of  this  instrument  Langley  has  examined  the 
emission-spectra  of  the  sun  and  moon,  and  of  solid  bodies 
between  o°  and  1500°,  whilst  flame,  arc,  and  absorption 
spectra  have  been  investigated  by  R.  v.  Helmholtz,2  Julius,3 
K.  Angstrom,4  Rubens,5  Snow,6  Lewis  and  Ferry,7  and 
Paschen.8 

The  red  and  infra-red  rays  were  for  long  believed  to  be 
incapable  of  photographic  action.  E.  Becquerel9  observed 
that  the  red  rays  affect  silver  chloride  which  has  been 
previously  exposed  to  light  for  a  short  time,  and  Draper 10 
succeeded  in  photographing  the  beginning  of  the  infra-red, 
but  complete  photographs  could  not  be  produced  until  Abney  " 
prepared  a  special  bromo-silver  emulsion  sensitive  to  the 
infra-red.  He  has  obtained  photographs  of  the  solar  spectrum 
up  to  wave-lengths  of  2700^,  both  with  a  prism  and  a  grat- 
ing, and  has  also  photographed  a  number  of  absorption- 
spectra. 

The  third  method  of  investigating  the   infra-red  is  based 


'  Sillim.  Journ.  [3]  21,  187;  [3]  27,    169;    (1886)  [3]  31;  32;    (1888)  36; 
(1889)  38.      Proc.  Amer.  Acad.  16,  342,     W.  A.  22,  598. 

Die  Licht-  und  Warmestrahlung  verbrennender  Gase.  (Berlin,  1890). 

Die  Licht-  und  Warmestrahlung  verbrannter  Gase  (Berlin,  1890). 

W.  A.  (1889)  36. 

W.  A.  45,  238. 

W.  A.  (1892)  46. 

Johns  Hopkins  Univ.  Circul.  (1894)  13,  74. 

8  W.  A.  (N.  F.)  50,  409;  (1894)  52,  209. 

9  A.  c.  p.  (1843)  [3]  9- 

10  P.  M.  (1843)  [3]  22. 

11  P.  T.  (1880)  171,  653;  (1886)  177.     P.  R.  S.  (i88i).31.     P.M.  [5]  3,  22. 


SPECTROSCOPIC  ADJUNCTS.      /  63 

on  E.  Becquerel's1  discovery  of  their  phophyrescent  action. 
A  layer  of  Balmain's  luminous  paint  is  exposed  to  diffused 
daylight,  and  then  to  the  infra-red  spectrum;  at  first  the 
spectrum  bands  become  brighter,  the  Fraunhofer  lines  re- 
maining unaltered;  this  soon  changes  and  the  Fraunhofer 
lines  gain  in  luminosity  until  they  appear  bright  on  a  dark 
ground.  The  results  obtained  in  this  manner  by  E.  and 
H.  Becquerel  agree  well  with  those  of  Langley  and  Abney. 

Lornmel2  has  improved  Becquerel's  method,  and  has  pre- 
pared photographs  of  the  infra-red  with  ordinary  plates.  The 
image  of  the  spectrum  is  obtained  in  the  manner  described, 
with  the  Fraunhofer  lines  bluish  and  luminous;  a  gelatine  dry 
plate  is  then  laid  over  the  image  on  the  phosphorescent  plate, 
and  all  the  details  are  clearly  reproduced.  Photographs  of 
the  grating  solar  spectrum  were  made  in  this  manner. 

The  grating,  particularly  the  concave  one,  in  combination 
with  a  prism,  is  especially  suitable  for  the  investigation  of  the 
infra-red,  since,  by  means  of  the  superposed  spectra,  the  wave- 
lengths in  this  region  may  be  compared  with  those  in  the 
visible  portion  which  are  accurately  known.  The  ordinary 
dispersion  formula  for  prisms  does  not  apply  to  the  infra-red 
region.3 

Observation  of  Absorption-spectra — The  object  under 
examination  is  placed  in  front  of  the  slit;  if  it  is  somewhat 
opaque,  direct  sunlight  is  used ;  the  electric  light,  Linnemann's 
zirconium  light,  Auer's  incandescent  burner,  a  good  petroleum 
lamp,  or  an  ordinary  Argand  burner  are  also  employed  as 
sources  of  illunrnation.  Daylight  is  convenient,  as  the 
Fraunhofer  lines  permit  of  ready  orientation,  but  it  is  unsuit- 


1  C.  r.  (1866)  63;  (1873)  77:  (1876)  83;  (1887)  104;  (1888)  107.  A.  c.  p. 
(1877)  [5]  10.  H.  Becquerel,  C.  r.  (1883)  96,  97;  (1884)  99;  (1886)  102.  A. 
c.  p.  (1883)  [5]  30. 

-  W.  A.  (1883)  20;  (1887)  30.  Sitzungsber.  Munchener  Akad.  (1888)  18; 
(1890)  20. 

s  Langley,  P.  M.  (1884)  [s]  17;  (1886)  22.  Sillim.  Journ.  [3]  27,  169.  W. 
A.  22,  598.  Desains  and  Currie,  C.  r.  (1880)  90;  (1882)  94. 


64  SPECTRUM  ANALYSIS. 

able  for  the  absorption-spectra  of  gases,  or  for  observations  in 
the  ultra-violet ;  in  these  cases  artificial  light  of  great  bright- 
ness is  necessary.  If  the  substance  under  examination  is  a 
gas,  it  is  placed  in  a  tube  with  plane  sides.  Glass  troughs 
with  plane  parallel  sides  are  used  for  liquids;  H.  W.  Vogel 1 
employs  ordinary  test-tubes,  placing  them  so  that  the  light- 
rays  pass  diametrically  through  to  the  slit,  and,  in  order  to 
overcome  the  difficulty  of  adjustment,  they  are  fixed  in  a 
rectangular  trough  of  water.  Gladstone  2  uses  a  wedge-shaped 
vessel  which  allows  all  the  absorbed  parts  to  be  observed  at  a 
glance;  as  a  substitute  Landauer 3  has  suggested  the  use  of 
the  ordinary  hollow  prism,  fixed  horizontally  or  vertically  in 
a  stand;  it  permits  of  the  rapid  observation  of  various  thick- 
nesses of  liquid,  and  is  particularly  well  suited  for  qualitative 
work  in  which  the  refractive  angle  of  the  vessel  may  be 
neglected.  The  absorption-spectrum  of  a  substance  depends 
on  its  concentration  and  the  thickness  of  the  column  through 
which  the  light  passes;  this  renders  its  accurate  characteriza- 
tion a  matter  of  difficulty,  and  is  only  possible  when  both  the 
above  factors  are  given.  Many  observers  have  confined 
themselves  to  giving  graphic  reproductions  of  selected  charac- 
teristic strong  and  faint  absorptions.  Kruss 4  suggested  the 
determination  of  the  "minimum  of  brightness";  this  is 
obtained  by  diluting  the  liquid  under  examination  until  the 
bands  whose  maxima  are  to  be  measured  are  readily  visible; 
their  limits  are  determined,  and  the  liquid  repeatedly  diluted, 
fresh  measurements  being  taken  after  each  addition  of  water; 
two  values  are  finally  obtained  which  closely  approximate  if 
the  liquid  is  further  diluted  and  the  minimum  of  brightness 
is  situated  between  them. 


1  Prakt.  Spectralanalyse  (Berlin,  1889). 

2  Jour.  Chem.  Socy.  Lond.  10,  79.      P.  M.  [4]  24,  417. 
8  Ber.  (1878)  11,  1773- 

4  Ibid.  16,  2051.     Zeitschr.  phys.  Chem.  2,  312.    Specielle  Methoden  der 
Analyse  (Hamburg,  1894). 


SPECTROSCOPIC  ADJUNCTS. 


Measuring  Appliances  and  Scales. — In  the  last  two 
chapters  the  measuring,  appliances  have  been  described  in 
detail  together  with  the  spectroscopes.  Simple  instruments 
with  a  prism  of  60°  have  a  millimeter  scale  reflected  into  the 
telescope;  generally,  following  Bunsen's l  suggestion,  the 
sodium  line  is  adjusted  to  the  5<Dth  division,  which  is  also  in  a 


750 


csn 


500 


w; 


Sr 


HgBra 


FIG.  38. 

line  with  the  fixed  edge  of  the  slit,  but  this  is  purely  optional: 
the  sodium  line  may  be  adjusted  on  any  other  division  so  long; 
as  the  spectrum  remains  within  the  limits  of  the  scale. 
Bunsen  2  in  his  earlier  work  had  the  sodium  line  at  the  looth 
division,  as  did  Lecoq  de  Boisbaudran  3  and  Kriiss,4  whilst 

1  P.  A.  119,  10. 

2  Ibid.  113,  377. 

3  Spectres  lumineux  (Paris,  1874). 

4  Ber.  19,  2742. 


66 


SPECTRUM  ANALYSIS. 


H.  W.  Vogel  adjusts  it  at  o,  and  gives  the  other  divisions  as 
-|-  or  —  according  to  their  greater  or  less  refrangibility.  The 
divisions  of  the  scale  are  usually  calculated  into  wave-lengths, 
and  the  results  given  as  such,  since  it  is  impossible  to  obtain 
spectroscopes  of  absolutly  identical  dispersive  power.  The 
conversion  is  most  readily  accomplished  by  means  of  an  inter- 
polation curve;  the  divisions  of  the  scale  are  plotted  as 
abscissae  on  paper  ruled  into  rectangular  spaces,  the  wave- 
lengths from  300-800^  form  the  ordinates,  and  the  points 
are  connected  by  means  of  a  smoothly  drawn  curve  as  shown 
in  Fig.  38,  so  that  the  interrelationship  of  wave-lengths  and 
scale  is  seen  at  a  glance.  The  table  is  completed  by  the 
•determination  of  the  position  of  the  following  lines  as  shown 
by  the  particular  spectroscope  employed,  their  wave-length 
is  given  in  Angstroms  (ten  millionths  of  a  millimetre),  and 
their  position  on  Kirchhoff  and  Bunsen's  old  scale  is  also 
added. 


Rowland's  Scale. 
Wave-length  in 

Angstroms. 

Flame-spectra.        Li 6708.2 

Na....  ...  \  5896'16  I  Mean 

(  5890.19  )          5893.2 

Tl 5350-6 

Mg 5183.9 

Sr 4607-5 

Fraunhofer  lines.   A 7607.8* 

B 6870.2 

C 6563.1 

Di 5896.16  | 

D2 5890.19  > 

E 5270.2* 

bi 5183-8 

b, 5172.9 

b3  and  b4  . .    5168.1* 

F 4861.5 

G 4308.0* 

H 3968.6 

K 3933-8 


Divisions  of 
KirchhofTs  Scale. 

31-8         \* 
50.0       /- 

67.8 

74-5 

105-5 

17-5 
28.9 
35-0 

50.0 

70.9 

74-5 

74-8 

75-0 

90.0 
127.3 
161.2 
165.7 


*  Mean  of  several  lines. 


SPECTROSCOPIC  ADJUNCTS.  6f 

Photographic  scales  showing  wave-lengths  directly  may 
be  prepared,  but  in.  certain  parts  the  divisions  are  so  close 
together  that  it  is  more  convenient  to  use  scales  with  equal 
divisions,  and  reduce  the  readings  to  wave-lengths.  Instead 
of  wave-lengths  their  reciprocals  are  sometimes  employed, 
that  is,  the  number  of  waves  in  i  cm.  at  o°  in  a  vacuum; 


this  value      r,  which   is   termed  the  oscillation  frequency,  is 

obtained  by  dividing  into  I  the  wave-lengths  reduced  to  o° 
and  a  vacuum,1  the  calculation  being  carried  to  six  or  seven 
figures;  some  observers,  including  Kayser  and  Runge,  use 
uncorrected  wave-lengths;  they  justified  this  on  the  ground 
that  the  refractive  index  of  air  was  not  known  with  sufficient 
accuracy,  and  that  the  increase  in  the  index,  as  the  wave- 
length decreases,  is  so  small  that  only  a  negligible  error  is 
introduced  by  regarding  it  as  constant;  for  example,  the 
difference  between  A  —  6000  and  A,  =  2200  is  only  0.09 
Angstrom.* 

Large  instruments,  with  several  prisms  automatically 
adjusted  to  the  position  of  minimum  dispersion,  have  a  divided 
circle  over  which  the  telescope  travels,  thus  giving  the 
measurements,  whilst  the  micrometer-screw,  which  moves  the 
last  prism,  is  utilized  for  the  same  purpose  in  the  case  of 
spectroscopes  in  which  the  rays  return  through  the  prisms, 
since  the  telescope  on  such  instruments  is  necessarily  fixed. 
None  of  these  appliances  give  more  than  approximations,  since 
it  is  difficult  to  obtain  the  mechanism  absolutely  exact,  and 
the  refractive  and  dispersive  power  of  the  prisms  are  affected 
by  the  temperature.  In  order  to  make  accurate  measure- 
ments with  prism  instruments  it  is  desirable  to  compare  them 
with  the  solar  spectrum,  or  with  that  of  iron;  both  are  rich  in 


1  B.  A.  R.  1878. 

8  Kayser  and  Runge,  A.  B.  A.  1893.       Hasselberg,  Ofvers.  K.  Vetensk, 
Akad.  Ftfrhandl.  (1892)  No.  9. 


68  SPECTRUM  ANALYSIS. 

lines  the  wave-lengths  of  which  have  been  accurately  deter- 
mined. 

Eder1  recommends  the  use  of  the  spark-spectrum  of  an 
alloy  consisting  of  equal  parts  of  cadmium,  zinc,  and  lead  for 
the  orientation  of  prism-spectra  of  medium  dispersion.  The 
most  accurate  ocular  observations  are  obtained  with  a  spec- 
trometer fitted  with  a  plane  grating  or  prism,  the  best  pho- 
tographic ones  with  a  concave  grating  spectroscope. 

Drawings  of  Spectra. — The  diagrammatic  reproduction  of 
spectra  are  made,  according  to  Bunsen's  suggestion,  on  paper 
with  printed  millimetre  scales;  the  breadth  of  the  lines  and 
bands  is  given  as  observed  in  the  spectroscope,  and  their 
relative  brightness  shown  by  the  varying  distance  of  the 
contour  from  the  horizontal;  such  drawings  are  shown  in 
Fig.  38,"  together  with  the  spectra  as  they  appear  in  the 
spectroscope. 

1  Denkschr.  der  Wiener  Akademie  (1893),  60. 

2  From  Wiedemann-Ebert,  Physikal-Practicum  (Braunschweig,  1893). 


CHAPTER  VI. 
SPECTRA. 

I.    EMISSION-SPECTRA. 

THREE  varieties  of  spctra  are  recognized,  continuous, 
channelled  or  band,  and  line  spectra.  Having  described  the 
production  of  spectra,  and  the  means  by  which  they  are 
examined,  it  is  necessary  to  consider  the  conditions  which 
modify  them,  and  also  the  laws  governing  their  construction ; 
much  light  has  been  thrown  on  these  subjects  by  more  recent 
investigations;1  indeed  spectroscopic  methods  appear  emi- 
nently suited  for  the  elucidation  of  the  molecular  structure  of 
matter,  since  change  in  a  spectrum  indicates  change  in  atomic 
motion.  All  substances  are  composed  of  molecules,  consist- 
ing of  similar  or  dissimilar  atoms,  the  number  of  which 
probably  varies  with  the  temperature  and  pressure;  the 
molecules  are  in  a  state  of  active  vibration,  but,  in  the  case  of 
solids,  are  maintained  in  proximity  by  their  mutual  attraction, 
the  vibrations  being  manifested  chiefly  as  heat.  The  mole- 
cules of  liquids  exert  sufficient  attraction  to  prevent  their 
complete  separation,  but  those  of  a  gas  are  independent;  their 
path  through  space  is  relatively  great  and  their  collisions 
comparatively  few. 

1  Kayser,  Spectralanalyse  (Berlin.  1883).  Spectralanalyse  in  Encyklo- 
padie  der  Naturwiss.  32.  (Handb.  der  Physik  von  Winkelmann.  Bres- 
lau,  1894,  p.  419.)  W.  A.  (1891)42.  Chem.  Ztg.  (1892)  16,  593.  Kayser 
and  Runge,  A.  B.  A.  1888-1894.  Rydberg,  Svenska  Vetensk.  Akad.  Handl. 
(1890)  23.  Deslandes,  C.  r.  (1886)  103,  375;  (1887)  104,  972.  Julius,  Ann. 
de  1'Ecole  polyt.  de  Delft,  1889.  Wiillner,  W.  A.  (1874)  8;  (1888)  34.  E. 
Wiedermann,  W.  A.  (1878)  5.  Schuster,  B.  A.  R.  1880.  Lockyer,  Studies 
in  Spectrum  Analysis  (London  and  New  York,  1878). 

69 


7O  SPECTRUM  ANALYSIS. 

In  addition  to  the  motion  of  the  molecule  as  a  whole, 
there  is  a  continuous  movement  of  its  parts ;  whilst  the  formerr 
except  for  the  velocity  and  extent  of  the  free  path,  is  the 
same  for  all  gases,  the  motion  of  the  atoms  must  be  different 
for  each  kind  of  molecule,  since  it  will  be  conditioned  by  the 
position,  number,  and  mass  of  the  atoms,  by  their  energy,  and 
by  the  nature  of  the  collision  of  different  molecules.  The 
vibrations  of  glowing  vapors,  which  we  perceive  as  light,  are 
conditioned  by  the  vibrations  of  the  atoms,  so  that  change  ia 
these  must  produce  alteration  in  the  spectra.  The  nature  of 
the  relationship  between  the  vibrations  of  the  atoms  and  the 
luminiferous  ether  are  unknown,  but  it  may  be  assumed  that 
the  wave-motion  of  the  latter  exhibit  the  vibrations  of  the 
former,  the  number  of  vibrations  of  an  observed  spectral  line 
corresponding  with  that  of  the  atom  itself.  Maxwell  showed 
that  only  the  majority  of  the  molecules  of  a  gas  are  at  its 
mean  temperature,  the  remainder  are  at  all  possible  intervals 
above  and  below  this,  so  that  the  spectrum  produced  at  a  par- 
ticular temperature  is  not  pure,  but  a  mixture,  with  those  rays 
predominating  which  correspond  with  the  mean  temperature. 

Solid  bodies  have  their  molecules  closely  adjacent,  the 
atoms  being  restrained  by  external  forces  from  producing 
their  own  vibrations,  and  this  proximity  causes  the  production 
of  all  possible  vibrations  if  the  collisions  increase  in  fre- 
quency; at  low  temperatures  the  vibntions  are  comparatively 
slow  and  produce  radiant  heat;  but  as  the  temperature  rises 
the  collisions  increase  in  violence  and  the  vibrations  in  fre- 
quency, producing  successively  the  infra-red,  the  red,  the 
yellow,  and  so  on,  until,  at  the  highest  temperatures,  the 
ultra-violet  is  obtained.  All  solids  therefore  exhibit  contin- 
uous spectra,  containing  rays  of  every  possible  wave-length ; 
the  same  applies  to  liquids,  so  far  as  they  can  be  caused  to 
emit  spectra.  The  circumstances  are  otherwise  with  luminous 
gases  and  vapors:  the  intervals  between  the  molecular  impacts 
are  relatively  long,  the  characteristic  individual  vibrations  of 


SPECTRA.  71 

the  atoms  are  able  to  develop,  and  the  corresponding  waves 
appear  in  the  spectrum,  which  is  therefore  discontinuous  and 
consists  of  separate  bright  regions.  Discontinuous  spectra 
are  divisible  into  band  and  line  spectra,  formerly  termed  by 
Pliicker  and  Hittorf 1  spectra  of  the  first  and  second  order. 
The  former  usually  consist  of  a  number  of  bands,  one  edge 
being  bright  and  gradually  diminishing  almost  to  darkness  in 
the  direction  of  the  other  edge;  they  resemble  to  some  extent 
illuminated  fluted  columns,  hence  the  name  channelled 
spectra,  which  is  also  applied  to  them.  Observed  under  high 
dispersions  the  channellings  are  resolved  into  numerous  slender 
lines,  arranged  regularly,  their  proximity  being  greatest  in  the 
brighter  regions.  Band-spectra  are  exhibited  by  compounds, 
and  also  by  elements  at  temperatures  below  that  necessary 
for  the  production  of  lines. 

Line-spectra  consist  of  separate  bright  lines  (slit  images) 
which,  if  produced  by  means  of  a  prism,  are  not  perfectly 
vertical,  but  are  slightly  inclined  towards  the  red;  they  are  far 
less  numerous  than  those  in  the  band-spectra,  and  appear  not 
to  exhibit  regularities  in  position  and  brightness.  The 
manner  in  which  they  change  into  the  very  different  band- 
spectra  has  not  been  explained ;  it  is  known  that  the  latter 
are  obtained  at  temperatures  intermediate  between  those 
required  for  the  production  of  continuous  spectra  and  line- 
spectra,  and  it  has  been  suggested  that  they  are  produced  by 
molecular  aggregates  which  would  be  expected  to  yield 
spectra  richer  in  lines  than  those  that  could  be  formed  in  the 
presence  of  fewer  atoms.  It  has  long  been  disputed  whether 
the  chief  portions  of  a  spectrum  are  constant  when  the  mole- 
cules remain  the  same.  Wullner2  decides  in  the  negative, 
and  holds  that,  with  unchanged  molecules,  the  emission  is  a 
function  of  the  temperature,  the  band-spectrum  being  pro- 

1  P.  T.  (1865)  155- 

2  W.  A.  (1879)  8;  (1888)  34.     Ber.  Berl.  Akad.  (1889)  38.    Comp.  also  his 
"  Lehrbuch  der  Physik." 


72  SPECTRUM  ANALYSIS. 

duced  at  low,  and  the  line-spectrum  at  high  temperatures; 
these  together  form  the  complete  spectrum  of  the  particular 
substance,  and  the  change  is  continuous.  The  opposite  view 
is  now  generally  accepted,  and  has  been  chiefly  developed  by 
Kayser;  according  to  this,  so  long  as  the  molecules  are 
unchanged  their  particular  vibrations  must  remain  constant, 
but  it  does  not  follow  that  at  any  temperature  they  should 
exhibit  all  their  possible  modes  of  vibration,  and  particularly 
not  with  equal  intensity.  It  has  been  repeatedly  observed 
that  increase  in  the  violence  of  impact  is  correlated  with 
greater  intensity  in  the  shorter  wave-lengths;  the  ultra-violet 
lines  become  considerably  stronger  if  the  arc  is  used  instead 
of  the  Bunsen  flame,  but  the  longer  waves  also  increase  in 
brightness,  lines  before  too  faint  to  be  seen  become  visible, 
and  there  is  a  general  increase  throughout  the  spectrum  in  the 
number  and  brightness  of  the  lines.  The  spontaneous  reversal 
of  the  lines  is  regarded  by  Kayser  as  a  definite  proof  of  the 
constancy  of  the  spectrum  within  each  order.  Light  from  a 
luminous  heated  gas  is  absorbed  by  cooler  gas  of  the  same 
kind,  but  as  the  same  rays  are  emitted  as  are  absorbed  by  the 
cooler  vapor  it  follows  that  the  wave-length  must  remain  un- 
changed, although  the  intensity  will  be  considerably  decreased 
and  the  original  bright  lines  be  replaced  by  dark  ones;  since 
such  reversal  occurs  without  alteration  between  all  attainable 
limits  of  temperature,  about  iooo°-5OOO°,  the  constancy  of 
the  emissions  throughout  the  same  range  is  established. 

Influence  of  Temperature  and  Pressure.— It  has  been 
stated  above  that  increase  in  temperature  produces  greater 
intensity  in  the  lines  within  the  particular  order  of  spectrum. 
Increase  in  the  pressure  is  accompanied  by  a  broadening  of 
the  lines; '  this  change  may  be  exhibited  by  all  substances  in 
varying  degree,  and  it  may  occur  symmetrically  or  only 
towards  one  side,  in  the  latter  case  generally  towards  the  least 

1  Comp.  Schuster,  B.  A.  R.  1880,  p.  275.   Roscoe  and  Schuster,  Spectrum 
Analysis  (London,  1885),  pp.  136,  163. 


SPECTRA.  «^r  73 


refrangible  end.  The  hydrogen  lines  may  be  extended  to 
such  a  degree  that  the  spectrum  becomes  continuous;  ' 
Zollner2  believed  that  this  was  due  to  the  density  of  the 
luminous  layer;  his  conclusion  was  deduced  from  KirchhorTs 
law,  but  it  is  not  in  agreement  with  the  observation  that  a 
Geissler  tube  exhibits  the  same  number  of  sharp  lines  whether 
viewed  longitudinally  or  transversely,  and  that  sharp  lines  are 
shown  by  the  solar  atmosphere  and  prominences  in  spite  of  the 
enormous  thickness  of  the  former.  General  acceptance  is 
now  given  to  Lockyer  and  Frankland's  3  view  that  the  increase 
in  breadth  is  due  to  greater  pressure,  although  the  tempera- 
ture also  exercises  some  influence;  but,  in  the  cases  under 
consideration,  a  rise  in  temperature  necessarily  produces  an 
increase  in  the  pressure.  The  theoretical  explanation  of  the 
phenomenon  is  as  follows:  so  long  as  the  molecules  vibrate 
singly  the  oscillations  occur  regularly  and  at  equal  intervals, 
and  therefore  produce  sharp  lines,  but  if  other  molecules  are 
in  close  proximity,  the  vibrations  are  disturbed  by  their 
impact,  the  frequency  of  which  depends  upon  the  pressure 
and  temperature.4 

Lockyer's  Long  and  Short  Lines. — Lockyer 5  has  devised 
a  method  which  readily  shows  the  influence  of  temperature 
and  pressure  on  a  spectrum.  The  arc  or  spark  is  adjusted 
horizontally  to  the  vertical  slit  of  the  spectroscope,  and  the 
image  thrown  on  to  the  slit  by  means  of  a  lens;  a  spectrum  is 
thus  obtained  exhibiting  long  and  short  lines  of  varying 
breadth:  that  shown  in  Fig.  39  is  produced  by  a  mixture  of 
calcium  and  strontium.  The  image  of  the  slit  corresponds 
with  that  of  a  section  of  the  arc,  the  middle  of  the  image 
showing  the  lines  in  the  middle  of  the  arc,  those  at  the  sides 

1  Frankland,  P.  R.  S.  (1868)  16,  416.     Wullner,  P.  A.  (1869)  137,  369. 

2  P.  A.  (1871)  142,  88. 

1  P.  R.  S.  (1869)  27,  288. 

4  Comp.  Lippich.  P.  A.  (1870)  139,  465. 

5  P.  T.  (1873)  163,  253,  639.     Galitzin,  W.  A.  (1895)  56,  78. 


74 


SPECTRUM   ANALYSIS. 


SPECTRA.  75 

of  the  latter  being  shown  at  the  extremities  of  the  image. 
The  luminous  vapor  is  both  hotter  and  denser  in  the  middle 
than  at  the  sides  of  the  arc;  therefore,  if  the  spectrum  is 
influenced  by  temperature  and  pressure,  the  middle  of  it 
should  differ  from  its  extremities,  and  this  is  actually  the  case. 
The  longer  lines  are  most  numerous  at  the  sides,  the  short 
ones  being  confined  to  the  middle;  all  taper  towards  their 
extremities;  moreover,  the  length  is  not  dependent  on  the 
brightness  of  the  lines,  as  the  fainter  ones  may  be  either  short 
or  long.  Lockyer  considers  that  the  longer  lines  are  produced 
at  lower  temperatures,  and  correspond  with  the  chief  lines 
observed  by  the  ordinary  method;  the  short  lines  are  due  to 
relatively  high  temperatures,  and  the  expansion  in  the  middle 
is  caused  by  the  greater  pressure  in  the  interior  of  the  arc. 

Influence  of  Magnetic  Current.  —  When  the  ZMines  are 
produced  by  means  of  a  Rowland's  grating,  and  a  Bunsen 
burner  and  sodium  chloride,  they  have  been  observed  by 
Zeeman  '  to  widen  during  the  passage  of  a  current,  if  the 
burner  is  placed  between  the  poles  of  an  electromagnet. 
With  an  oxy-coal  gas-flame  they  expanded  to  three  or  four 
times  the  normal  width.  Similar  results  were  obtained  with 
a  lithium  line.  Interruption  of  the  current  produced  an 
immediate  reversion  to  the  ordinary  state.  The  widening 
was  also  observed  in  the  absorption-lines  (reversed  lines) 
produced  by  sodium  vapor,  in  a  porcelain  tube  placed  between 
the  poles  and  perpendicular  to  a  line  joining  them.  The 
widening  is  not  due  to  change  in  the  density  of  the  luminous 
or  absorptive  gases,  but  the  observations  confirm  Lorentz's 
theory,  according  to  which  electrical  phenomena  are  con- 
ditioned by  the  position  and  motion  of  electrically  charged 
ions,  by  which  also  light  vibrations  are  accomplished.  Zeeman 
deduces  from  this  theory  the  proposition  that  the  broadened 

1  Zittungsverl.  K.  Akad.  Wet.  Amsterdam  (1896-97),  pp.  181-242.  W. 
A.  Beibl.  (1897)  21,  139.  Astrophys.  J.  (1897)  5,  332.  P.  M.  (1897)  [5]  43, 
226. 


UNIVERSITY 


\ 


76  SPECTRUM  ANALYSTS. 

spectrum-lines  of  a  light-ray,  in  the  direction  of  the  magnetic 
current,  are  subjected  to  circular  polarization,  one  extremity 
to  the  left,  the  other  to  the  right.  If  the  ray  is  at  right 
angles  to  the  current,  both  extremities  are  linearly  polarized, 
at  right  angles  to  its  direction. 

II.    ABSORPTION-SPECTRA. 

Kirchhoff's  Law. — Fraunhofer,  in  1824,  observed  the 
coincidence  of  the  yellow  sodium  lines  with  the  double  ZMines 
of  the  solar  spectrum,  and  the  relationship  between  the  emis- 
sion and  absorption  of  light  had  been  previously  suggested  by 
various  workers,1  but  Kirchhoff 2  in  1859  enunciated  and  estab- 
lished the  law  which  bears'his  name,  and  which  is  also  known 
as  the  "  law  of  exchanges."  In  order  to  directly  prove  the 
coincidence  of  the  above  lines  Kirchhoff  observed  a  moderately 
bright  solar  spectrum  through  a  sodium  flame  which  was  placed 
before  the  slit;  the  dark  lines  were  at  once  changed  to  bright 
ones,  but  with  a  very  bright  solar  spectrum  the  lines  were 
darker  than  when  viewed  directly.  He  then  examined  the 
Drummond  lime-light  through  the  sodium-flame,  and  got  dark 
lines  in  place  of  the  yellow  ones,  showing  that  the  sodium- 
flame  absorbs  the  same  kind  of  rays  that  it  emits.  The  results 
of  these  experiments,  and  certain  theoretical  consideration^, 
led  him  to  propo  -^d  the  generalizationfthat  the  relationship^ 
between  the  emissive^and  absorptive  power  of  allsubstances 
Tor  light  of  the  same  wave-length  is  identical  ~at  the  same 
jtemperature.  The  absorption-speciruTnoTa  substance  corre- 
sponds  therefore  with  its  emission-spectrum  at  the  same  tem- 
perature and  in  the  same  molecular  condition.  This  was 
proved  by  Kirchhoff  and  Bunsen  in  the  case  of  sodium  and 

1  Angstrom.    P.  A.    (1853)   94,    141.       Foucault,    Bull.   Soc.   philom.  de 
Paris,  1849.     A.  c.  p.  (1860)  [3]  58,  476.     Stokes,  P.  M.   (1860)  [4]  20,   20. 
Balfour  Stewart,  T.  R.  S.  E.  1858. 

2  A.  B.  A.  1861,  p.  64. 


SPECTRA.  77 

other  volatile  metals,  and  by  Cornu,1  Liveing  and  Dewar,2  and 
Lockyer 3  for  others,  including  those  that  are  most  refractory. 
Kirchhoff's  investigation  finally  proved  the  nature  and  origin 
of  the  Fraunhofer  lines  (comp.  Chapter  IX).  Gases  and 
vapors  at  low  temperatures  show  absorption-spectra  consisting 
of  bands,  but  at  higher  temperatures  they  are  composed  of 
lines;  as  a  rule  the  absorption-spectra  of  solids  and  liquids  are 
continuous  over  a  large  portion  of  the  field,  corresponding 
with  their  continuous  emission-spectra;  the  spectroscopic 
investigation  of  substances  thus  becomes  possible  at  a  tem- 
perature below  that  at  which  they  are  luminous. 

Kirchhoff's  law  indicates  that  the  luminosity  of  bodies  is 
due  to  increase  in  their  temperature.  Objection  has  been 
made  to  this  by  more  recent  investigators;  thus  E.  Wiede- 
mann  4  has  shown  that,  apart  from  the  normal  evolution  of 
light,  causes  other  than  rise  in  temperature  may  produce 
luminosity  in  a  body,  and  to  this  luminescence  he  considers 
that  Kirchhoff's  law  does  not  apply.  Hittorf5  and  W.  v. 
Siemens6  have  also  shown  that,  up  to  a  temperature  of  about 
2000°,  gases  emit  no  light,  whilst  Pringsheim  7  believes  that 
vapors  cannot  become  luminous  by  increase  of  temperature 
alone,  but  only  in  consequence  of  undergoing  chemical 
change.  At  present  it  is  not  possible  to  say  how  far  these 
objections  are  justified;  even  if  correct  they  do  not  necessarily 
invalidate  the  law  of  exchanges,  which  has  received  support 
from  the  theory  of  resonators.  The  mechanism  of  light 
absorption  is  as  yet  far  from  being  completely  understood. 

Influence  of  Temperature  and  Physical  State. — Absorp- 
tion-spectra are  usually  observed  at  low  temperatures,  thus 

C.  r.  (1871)  73,  332. 

P.  R.  S.  28. 

Studies  in  Spectrum  Analysis  (London  and  New  York,  1878). 

W.  A.  (1888)  34,  446. 

Ibid.  (1879)  7;  (1883)  19. 

Ibid.  (1883)  18. 

Ibid.  (1892)  45. 


78  SPECTRUM  ANALYSIS. 

readily  permitting  the  determination  of  the  influence  of  the 
molecular  constitution.  The  absorption-spectra  of  iodine  in 
the  solid  form,  in  solution,  and  in  the  gaseous  state  are  all 
different;  indeed  in  the  latter  state  it  exhibits  a  line  and  a 
band  spectrum  corresponding  with  its  two  emission-spectra. 
A  rise  in  temperature  causes  an  increase  in  the  absorption 
within  the  same  order  of  spectra. 

H.  W.  Vogel 1  found  that  if  solutions  of  organic  dyes  are 
volatilized  on  glass  plates,  the  residue  usually  exhibits  a 
different  spectrum  from  that  of  the  solution,  but  the  latter 
remains  unchanged  if  gelatine,  glue,  starch,  or  gum  arabic  is 
added  to  the  solutions  before  drying.  Stenger2  states  that 
in  the  gelatine  film  the  molecular  aggregation  is  the  same  as 
in  solution,  hence  the  identity  of  spectrum;  in  its  ordinary 
solid  state  the  dye  is  composed  of  more  complex  molecules 
and  therefore  has  a  different  absorption-spectrum. 

Influence  of  the  Solvent. — Solutions  of  substances  which 
exhibit  absorption-spectra  consisting  of  bands  frequently 
show  no  regularity  in  the  changes  which  occur  when  other 
solvents  are  employed.  In  this  connection  Kundt3  has  pro- 
pounded the  following  rule,  which,  however,  is  not  of  uni- 
versal application:  comparing  two  colorless  solvents  which 
differ  considerably  in  refractive  and  dispersive  power,  the  one 
in  which  these  are  greater  will  cause  the  absorption-bands  to 
approach  the  red  end  of  the  spectrum.  Stenger4  accounts 
for  the  exceptions  to  the  above  rule  by  suggesting  that  the 
spectrum  of  a  substance  is  dependent  both  on  its  chemical 
composition  and  on  its  molecular  state;  if  the  physical  mole- 
cules in  the  solution  are  identical  with  the  chemical  ones,  the 
body  follows  Kundt's  rule,  but  solutions  frequently  contain 
aggregates  composed  of  a  number  of  chemical  molecules. 

1  Ber.  Berl.  Akad.  1878,  p.  409. 
8  W.  A.  (1888)  33.583. 

3  P.  A.  Jubelband  (1874)  p.  615.     W.  A.  (1878)  4,  34. 

4  W.  A.  (1888)  33,  577. 


SPECTRA.  79 

The  deviation  from,  or  agreement  with  the  rule  may  also  be 
due  to  the  varying  extent  to  which  the  substance  in  solution 
undergoes  electrolytic  dissociation. 

Influence  of  Optical  Density.1 — The  influence  of  concen- 
tration and  of  the  thickness  of  the  layer  of  substance  has  been 
already  considered  in  the  preceding  chapter.  The  experi- 
ments of  Bunsen  and  Roscoe  2  show  (i)  that  the  quantity  of 
light  absorbed  by  a  layer  of  infinite  thickness  is  proportional 
to  the  quantity  (intensity)  of  the  incident-rays.  (2)  The 
quantity  of  light  absorbed  is  dependent  on  the  density  of  the 
absorbent.  The  coefficient  of  absorption,  calculated  from  these 
data,  gives  the  relationship  in  intensity  between  the  incident 
and  emergent  rays  for  a  layer  of  unit  thickness;  in  place  of 
this,  Bunsen  and  Roscoe  employ  the  coefficient  of  extinction, 
which  facilitates  the  calculation  of  the  concentration  from  the 
absorption;  the  term  is  applied  to  the  reciprocal  of  the  thick- 
ness of  substance  required  to  reduce  the  light  to  one  tenth  of 
its  original  intensity. 

Fluorescence  and  Absorption. — Absorption  of  light  is 
connected  with  phosphorescence  and  fluorescence.  Certain 
substances  become  luminous  by  the  action  of  light;  if  the 
luminosity  ceases  on  the  withdrawal  of  the  light,  they  are  said 
to  be  fluorescent,  whilst  the  term  phosphorescent  is  applied  to 
substances  which  continue  to  be  luminous  after  the  light  is 
cut  off.  Hitherto  fluorescence  has  only  been  observed  in  the 
case  of  liquids,  and  phosphorescence  in  that  of  solids.  In 
accordance  with  the  law  of  the  conservation  of  energy,  the 
rays  causing  these  phenomena  are  absorbed ;  fluorescent 
bodies  exhibit  corresponding  absorption-spectra,  and,  as  they 
absorb  the  ultra-violet  rays  more  or  less  completely,  they  all 
fluoresce  in  this  region  of  the  spectrum. 

1  Comp.  O.  Knoblauch,  W.  A.  (1891)  43,  738. 
8  P.  A.  (1857)  101,  235.   - 


80  SPECTfi UM  ANALYSIS. 

III.     RELATIONSHIP    BETWEEN   THE    LINES    OF   AN    ELEMENT. 

Observation  of  different  elements  shows  that  some  have 
lines  distributed  throughout  the  whole  spectrum  field,  whilst 
others  exhibit  only  a  few  single  lines  or  groups,  so  regularly 
arranged  as  to  suggest  the  idea  of  a  definite  relationship. 
Early  investigations  led  to  the  conclusion  that  an  acoustical 
law  could  be  applied  to  the  luminiferous  vibrations  of  the 
molecules;  a  string  vibrating  as  a  whole  gives  a  fundamental 
note,  but  if  it  vibrates  in  parts  the  number  of  vibrations  in 
the  notes  produced  is  2,  3,  4,  etc.,  times  that  of  the  funda- 
mental note;  if  this  Jaw  applies  in  optics,  the  wave-length  of 
the  different  lines  of  a  spectrum  must  bear  a  mutual  ratio 
represented  by  whole  numbers. 

The  first  attempt  to  discover  such  regularities  was  made 
by  Lecoq  de  Boisbaudran  '  in  the  case  of  the  nitrogen  lines; 
his  conclusions  were  based  on  wave-length  determinations  of 
insufficient  accuracy,  aqd  were  not  confirmed  by  Thalen. 
Stoney2  was  more  successful,  and  showed  that  the  ratio  of  the 
hydrogen  lines  C  :  F  :  h  —  20  :  27  :  32 ;  the  subject  was 
further  investigated  by  Stoney  and  Reynolds,3  Soret,4  and 
others,  until  the  more  thorough  work  of  Schuster6  rendered 
the  theory  no  longer  tenable.  He  showed  that,  even  when 
there  is  absolutely  no  connection  between  the  lines,  the 
chances  are  in  favor  of  a  harmonic  relationship  in  spectra 
rich  in  lines,  and,  whilst  many  facts  indicate  the  existence 
of  a  mutual  relationship  between  the  wave-lengths,  the  law 
which  it  follows  is  as  yet  undiscovered.  The  subject  ceased 
to  attract  attention  for  several  years  until  Balmer6  published 
a  formula  which  reproduces  with  wonderful  accuracy  the  posi- 

C.  r.  (1869)  69,  694. 

P.  M.  (1871)  [4]  41,  291. 

Ibid.  (1871)  [4]  42,  41. 

Ibid.  [4]  42,  464. 

B.  A.  R.  1880.     P.  R.  S.  (1881)  31,  337. 

W.  A.  (1885)  25,  80. 


SPECTRA.  8 1 

tion  of  the  hydrogen   lines.     The  values  are  given  by  the 
expression 


»'  -  4 

n  is  a  whole  number  between  3  and  15,  A  a  constant,  3645.42 
Angstroms  according  to  Cornu's  measurements,  or  3647.20 
taking  Ames*  more  accurate  determinations;  the  possible 
error  in  the  latter  is  only  0.1-0.3  Angstroms,  and  the  agree- 
ment between  the  observed  wave-lengths  and  those  calculated; 
from  the  above  formula  is  within  these  limits.  Cornu,1 
simultaneously  with  Balmer,  pointed  out  that  the  wave-length 
of  the  readily  reversible  lines  of  aluminium  and  thallium  bear 
a  definite  relation  to  those  of  hydrogen,  whilst  a  few  years 
later  Deslandres2  gave  a  formula  for  the  lines  composing  the 
bands  of  numerous  elements. 

In  1887  Kayser  and  Runge  3  commenced  their  investiga- 
tions, and  succeeded  in  obtaining  a  formula  which  reproduces, 
"series"  in  the  case  of  a  considerable  number  of  elements; 
Balmer's  formula  for  the  hydrogen  lines  is  only  a  special 
instance  of  their  more  generalized  expression.  The  term 
"series"  is  applied  to  related  lines,  which  are  particularly 
numerous  in  the  spectra  of  the  metals  of  the  alkalis  and 
alkaline  earths.  Attention  had  bfeeri^called  to  these  by  Live- 
in%  and  Dewar  *  before  the  publication  of  Balmer's  work.  The 
distance  between  two  consecutive  lines  decreases  with  dimin- 
ishing wave-length,  so  that  the  lines  asymptotically  approach 
a  limit;  they  applied  the  term  '*  harmonic  "  to  such  a  series 
of  similar  groups.5  Taking  th^-  refractive  index  of  air  as  con- 

1  C.  r.  (1885)  100,  ii8i. 

2  Ibid.  (1886)  103,  375;  (1887)  104,  972. 

3  Ueber  die  Spectren  der  Elemente  A.  B.  A.  1888,  1889,  1890, 1891,  1892, 
1893.     W.  A.  (1894)  52,  114.   Runge,  B.  A.  R.  1888,  p.  576.   Kayser,  Chem. 
Ztg.  (1892)  16,  533.    Encyklopadie  der  Naturw.  32  (Winkelmann's  Handb. 
der  Physik.     Breslau,  1894)  p.  429. 

4  P.  T.  1883,  p.  213,  and  also  previously. 

5  Ibid.  1884. 


82  SPECTRUM  ANALYSIS. 

stant,  a  value  proportional  to  the  number  of  waves,  i.e.,  the 
reciprocal,  was  used  by  Kayser  and  Runge  in  place  of  the 
wave-length;  thus  modified  Balmer's  formula  becomes 

-  =  A  +  Bn~2,  and  then  T  =  A  +  Bn~2  +  Cn~*. 

A  A 

This  expression  gives  only  an  approximation;  probably  the 
number  of  waves  is  only  a  function  of  n  which,  in  the  nega- 
tive power,  admits  of  the  development  of  a  rapidly  conver- 
gent series;  of  these  the  first  three  terms  are  sufficient  to  give 
their  values  with  remarkable  accuracy.  Kayser  and  Runge 
then  extended  their  investigations  so  as  to  elucidate  the  fol- 
lowing questions:  the  applicability  of  the  formulae  in  the  case 
of  measurements  of  the  highest  possible  degree  of  accuracy; 
whether  lines  of  wave-lengths  indicated  by  the  formulae  really 
•exist;  can  all  the  lines  of  every  element  be  reduced  to  series? 
•can  a  relationship  be  shown  between  the  constants  of  the 
formulae  of  different  elements  ? 

The  investigators'  objects  could  not  be  attained  by  the 
tise  of  the  older  wave-length  measurements,  partly  on  account 
of  their  inaccuracy,  partly  because  they  did  not  include  the 
ultra-violet,  so  that  it  became  necessary  to  re-examine  the 
spectra  of  the  elements  with  the  highest  possible  degree  of 
accuracy.  The  largest  number  of  series  represented  by  the 
above  formulae  are  exhibited  by  the  spectra  of  the  members 
of  Mendeleeffs  first  three  groups.  The  metals  sodium, 
potassium,  rubidium,  caesium,  copper,  silver,  aluminium, 
indium,  and  thallium  each  have  two  series  in  which  B  and  C 
are  identical  and  A  differs;  two  such  series  may  therefore  be 
regarded  as  a  series  of  pairs  of  lines,  each  pair  having  the 
same  difference  in  vibration.  Probably  all  elements  have  two 
such  series  of  pairs.  The  first  series  contains  strong,  ill- 
defined  lines,  and  is  termed  the  first  "subseries  "  ;  the  second 
series  contains  well-defined  fainter  lines,  sometimes  broaden- 


SPECTRA.  83 

ing  out  towards  the  red :  they  form  the  second  subseries.  The 
two  subseries  were  not  observed  in  the  spectra  of  rubidium 
and  caesium;  lithium  exhibits  both  series,  but  they  consist  of 
single  lines  instead  of  pairs.  The  difference  in  wave  in  both 
series  is  practically  identical  in  the  case  of  each  element,  and 
bears  a  relationship  to  its  atomic  weight.  The  alkali  metals 
have  a  third  series  which  includes  the  strongest  and  most 
readily  reversible  lines  of  the  whole  spectrum,  and  is  called 
the  "  principal  series  "  ;  in  the  spectrum  of  lithium  it  consists 
of  single  lines,  in  the  other  metals  of  pairs;  these  are  closely 
adjacent  in  the  case  of  sodium,  but  with  increasing  atomic 
weight  the  separation  becomes  greater,  whilst  the  entire 
series  gradually  approaches  the  least  refrangible  portion  of 
the  spectrum.  In  each  pair  the  stronger  line  has  the  smaller 
wave-length;  this  was  already  known  to  be  true  of  the  sodium 
jtMines.  Within  each  principal  series  the  difference  in  the 
number  of  waves  between  the  pairs  is  approximately  inversely 
proportional  to  the  fourth  power  of  the  ordinal  number.  The 
largest  positive  value  given  by  the  formulae  for  all  series 
hitherto  observed  corresponds  with  the  ordinal  number  3;  the 
lines  where  n  =.  3  are  comparable  with  fundamental  notes, 
since  they  represent  the  longest  possible  waves,  exactly  as 
exhibited  in  Balmer's  formula  for  the  hydrogen  lines. 

The  spectra  of  copper,  silver,  and  gold  do  not  show  such 
striking  regularities  as  those  of  the  alkali  metals,  which 
appear  all  to  be  arranged  on  one  plan.  By  analogy  with  the 
order  observed  in  other  spectra  the  existence  in  the  spectra  of 
copper  and  silver  of  both  subseries  of  pairs  can  be  demon- 
strated ;  but  this  is  not  so  with  gold,  possibly  because  the 
series  become  fainter  as  the  atomic  weight  increases. 

Magnesium,  calcium,  and  strontium,  amongst  the  alkaline 
earths,  have  spectra  with  two  subseries  consisting,  not  of 
pairs,  but  of  triplets  with  a  constant  difference  of  wave:  as 
the  atomic  weight  increases  the  series  diminish  in  intensity  and 
approach  the  red  end  of  the  spectrum.  This  probably  ex- 


84  SPECTRUM  ANALYSIS. 

plains  why  no  series  could  be  found  in  the  case  of  bariumr 
the  last  element  in  this  group. 

The  spectra  of  zinc,  cadmium,  and  mercury  also  exhibit 
two  subseries  of  triplets,  but  scarcely  half  the  total  number  of 
lines  is  included  in  the  series. 

Only  a  few  of  the  elements  in  Mendeleeff's  fourth  and 
fifth  groups  have  been  available  for  Kayser  and  Runge's  in- 
vestigations, which  have  been  confined  to  tin  and  lead  in  the 
former,  and  to  arsenic,  antimony,  and  bismuth  in  the  latter; 
the  regularities  found  in  the  members  of  the  first  three  groups 
could  not  be  detected  in  these.  Each  spectrum  is  character- 
ized by  a  large  group  of  lines  which  are  repeated  in  such  a 
way  that,  by  the  introduction  of  a  constant,  the  number  of 
waves  of  one  group  may  be  deduced  from  that  of  another, 
but  the  lines  do  not  permit  of  arrangement  into  series,  and 
their  appearance  gives  no  clue  as  to  their  possible  interrela- 
tionship. It  is  not  surprising  that  all  the  lines  of  a  spectrum 
do  not  fall  into  series,  for  in  order  to  compare  different 
elements  they  should  be  investigated  under  the  same  relative 
conditions,  and  not  at  the  same  temperature.  Failing  accu- 
rate knowledge  of  the  temperatures  at  which  the  elements 
would  be  in  a  uniform  molecular  condition,  it  may  be  assumed 
that  those  of  high,  melting  and  boiling  point  would  require  a 
much  hotter  flame  than  the  more  volatile  ones;  consequently 
if  an  arc  lamp,  giving  a  temperature  of  3OOO°-35OO°,  is  required 
in  order  to  produce  the  complete  series  in  the  case*  of  the 
readily  fusible  alkali  metals,  it  follows  that,  with  the  other 
elements,  the  higher  the  melting-point  the  less  characteristic 
will  the  series  be. 

Working  independently  of  Kayser  and  Runge,  Rydberg1 
simultaneously  adopted  the  same  view  of  the  structure  of 


1  C.  r.  (1890)  11O,  394.  Zeitschr.  physikal.  Chern.  (1890)  5,  227.  Svenska 
Vetenskap.  Akad.  Handlingar  Stockholm  (1890),  23,  No.  n.  W.  A.  (1893) 
50,  629;  (1894)  52,  119. 


\ 


SPECTRA.  85 

line-spectra;  he  employed  the  number  of  waves  instead  of 
the  wave-length,  and  his  investigations  of  the  members  of  the 
first  three  groups  of  the  periodic  system  led  him  to  conclude 
that  the  "long"  lines  form  pairs  or  triplets  which,  in  the  case 
of  each  element,  are  characterized  by  a  constant  difference  (v) 
in  the  number  of  waves  of  the  components.  In  each  group 
of  elements  this  value  increases  in  a  ratio  somewhat  exceed- 
ing the  square  of  the  atomic  weight.  The  triplets  occur  in 
the  first  and  third  groups,  the  valency  of  which  is  odd;  the 
components  of  the  double  lines  form  series,  the  members 
being  functions  of  consecutive  whole  numbers;  each  series  can 
be  approximately  reproduced  by  the  expression 


where  n  is  the  number  of  waves,  m  any  whole  number,  the 
ordinal  number  of  the  member,  and  NQ  =  109721.6,  a  con- 
stant applicable  to  all  the  series  of  every  element,  and  which 
is  obtained  from  Balmer's  formula;  n0  and  /*  are  constants 
peculiar  to  each  series,  n0  being  the  limit  which  the  number 
of  waves  n  approaches  if  m  is  infinite.  Like  Kayser  and 
Runge,  Rydberg  distinguishes  three  kinds  of  series,  "nebu- 
lous," "sharp,"  and  ''principal";  the  first  two  are  composed 
of  pairs  or  triplets,  so  that  the  elements  of  the  first  and  third 
groups  have  four  different  series  of  these  two  kinds,  and  the 
elements  of  the  second  group  have  six;  they  are  termed  the 
first,  second,  and  third  nebulous  or  sharp  series;  the  lines  of 
the  first  series  of  either  kind  are  the  strongest  and  least 
refractive.  In  the  case  of  the  elements  in  group  one,  the 
principal  series  contains  the  strongest  lines  of  the  spectrum, 
the  nebulous  series  are  next  in  order,  and  the  sharp  series 
the  faintest;  in  both  the  separate  groups  and  series  the 
intensity  of  the  light  decreases  as  the  ordinal  number  rises. 
The  different  series  of  an  element  are  sufficiently  related 


86  SPECTRUM  ANALYSIS. 

to  show  that  they  all  belong  to  one  system  of  waves;  the 
series  of  the  same  group,  nebulous  or  sharp,  have  the  same 
value  for  //;  the  difference  of  the  n0  value  is  equal  to  v  or  vl 
and  ^2;  the  series  of  the  same  order,  first,  second,  or  third, 
have  the  same  value  for  n0  in  the  different  groups,  but  differ 
in  that  for  yw.  The  wave-length  and  the  corresponding  number 
of  waves,  the  values  of  the  constants  v,  n0,  and  p  of  the  corre- 
sponding series  in  the  various  elements,  are  periodic  functions 
of  the  atomic  weight;  the  periodic  difference  in  the  constants 
permits  of  the  calculation  of  the  spectrum  of  an  element  if 
the  spectra  of  the  elements  adjacent  to  it  in  the  periodic 
system  are  known. 

Rydberg's  investigations  have  strengthened  the  arguments 
in  favor  of  a  single  system  of  waves,  and  indicate  the  possi- 
bility of  representing  all  the  lines  of  a  spectrum  by  a  single 
formula,  but  they  are  opposed  to  the  idea  of  a  mixed  spec- 
trum such  as  would  be  produced  by  molecules  at  varying 
temperatures.  He  considers  it  probable  that  each  element 
possesses  only  a  single  spectrum,  and  that  the  intensity  of 
the  series  and  of  the  special  lines  varies  with  the  temperature 
and  density  of  the  luminous  gas,  in  a  manner  similar  to  the 
changes  in  the  overtones  of  a  bell.  The  arrangement  of 
band-spectra  suggests,  even  more  strongly  than  line-spectra, 
the  possibility  of  their  structure  conforming  to  definite  rules; 
Lecoq  de  Boisbaudran  '  and  Thalen  2  pointed  out  certain 
regularities,  but  these  did  not  permit  of  the  deduction  of  a 
law  which  was  first  formulated  by  Deslandres.3  The  lines  of 
a  band  form  series  of  similar  lines,  the  series  being  connected 
in  such  a  manner  that,  in  each  one,  the  distances  between  two 
consecutive  lines  are  approximately  in  arithmetical  progres- 
sion. If  the  edge  of  a  band  is  designated  by  o  and  the  follow- 

1  C.  r.  (1869)  69. 

2  Svenska.  Vetensk.  Akad.  Handl.  (1869)  8. 

3  C.  r.  (1886)  103,  375;  (1887)   104,  972.      A.   c.   p.  (1888)  [6]  15.     J.  de 
Phys.  (1890)  [2]  10,  276. 


SPECTRA.  87 

ing  lines  by  the  succeeding  numbers  I,  2,  3,  .  .  .  n,  then  the 
number  of  waves  of  the  nth  line  is  given  by  the  formula 


-  n 

"•n 

where  a  is  the  number  of  waves  of  the  edge,  and  b  the  differ- 
ence between  this  and  the  number  of  waves  of  the  first  line. 
The  different  bands  of  a  spectrum  are  related  in  such  a  manner 
that  the  first,  second,  etc.,  edges  of  all  are  represented  by  the 
expression 

I  =  A  +  B  +  Cn\ 

corresponding  with  that  representing  the  lines  of  a  series; 
A,  By  and  C  are  constants,  and  n  progressive  numbers.  The 
absolute  validity  of  these  laws  is  questioned  by  Kayser  and: 
Runge,1  but  maintained  by  Deslandres.  Theoretical  articles 
on  the  origin  of  lines,  pairs,  etc.,  have  been  published  by 
Lecoq  de  Boisbaudran,2  Stoney,3  Julius,4  and  v.  Kovesligethy.* 


IV.     RELATIONSHIP     BETWEEN    THE    SPECTRA   OF   DIFFERENT 

ELEMENTS. 

Attention  was  first  directed  to  this  subject  by  Lecoq  de 
Boisbaudran6  in  1869;  he  pointed  out  the  similarities  in  the 
structure  of  the  spectra  of  potassium,  rubidium,  and  caesium, 
and,  applying  the  term  *'  homologous  "  to  certain  analogous 
lines  in  each,  he  concluded  that  in  the  case  of  the  metals  of 
the  alkalies  and  alkaline  earths  the  spectra  -approximate  the 
red  as  the  atomic  weight  increases.  This  has  been  confirmed 

A.  B.  A.  1889. 

C.  r.  (1869)  69,  445,  606,  657. 

P.  M.  (1871)  [4]  41.     Trans.  Dubl.  Soc.  (1891)  [2]  4.   P.  M.  (1892)  [5]  33. 

Ann.  de  1'ecole  polyt.  de  Delft  (1889),  5. 

Theor.  Spectralanalyse  (Halle,  1890). 

C.  r.  (1889)  69,  610. 


SPECTRUM  ANALYSIS. 


by  later  and  more  exact  measurements.  He '  subsequently 
employed  these  homologous  lines  for  the  calculation  of  the 
atomic  weights  of  gallium  and  germanium,  which  had  not  then 
been  determined;  his  method  was  based  upon  the  rule  which 
he  had  enunciated,  that  within  the  groups  of  the  periodic 
system  the  variation  in  the  increase  of  the  atomic  weight  is 
proportional  to  that  of  the  increase  in  the  wave-length  of  the 
homologous  lines.  The  following  is  an  example  of  the 
method  of  calculation: 


Atomic 
Weight. 

Difference. 

Difference. 

Variation. 

Mean  Wave- 
length of 
Two  Lines. 

Diff. 

Variation. 

Si.. 
Ge.. 

Sn.. 

Al.. 

Ga.. 
In.. 

28.0 
n 

118.0 
27-5 
69.9 

II3-5 

90.0 
Between 
Si  and  Sn 

42.4 
43-6 

1.2 

1.2    _  2.8302 

4010 
4453 

5077 
3952 

4101 
4306 

443 

624 

149 
205 

40.51 

100 
IOO 

42.4         100 

The  fraction  -         :  means  that  in  order  to  obtain  43.6, 
i  oo 

2.8302  per  cent  of  the  difference  42.4  must  be  added;  the 
variation  (x)  for  the  group  Si,  Ge,  Sn  is  obtained  from  the 
ratio  37.584  :  2.8302  ::  40.51  :  x  —  3.051  per  cent;  the  in- 

oo 

crease  (y)  in  atomic  weight  from  Si  to  Ge  =  — =  44.32, 

2.03051 

and  therefore  the  atomic  weight  (n)  of  germanium  =  72.32. 
Kayser3  considers  that,  whilst  the  above  rule  perhaps  contains 
a  nucleus  of  truth,  it  is  at  present  not  applicable,  and  requires 
a  knowledge  of  atomic  weights  considerably  exceeding  in 
accuracy  almost  all  the  current  values.  In  consequence  of 
this  Ames3  was  unable  to  apply  the  rule  to  magnesium,  zinc, 

1  C.  r.  86,  943;  (1886)  102,  1291.     Ber.  19,  4790. 

9  Spectralanalyse,     in    Encyklopadie    der    Naturw.    32    (Winkelmann, 
Physik.     Breslau,  1894)  p.  440. 
3  P.  M.  (1890)  [5]  30. 


SPECTRA.  89 

and  cadmium,  although  his  fundamental  homologous  lines  were 
correctly  selected;  since  the  selection  of  homologous  lines 
is  to  some  extent  arbitrary,  the  close  agreement  in  the  calcu- 
lated values  for  gallium  and  germanium  must  have  been  partly 
due  to  chance.  Ditte,1  Troost  and  Hautefeuille,2  Ciamician,3 
Hartley,4  Ames,6  and  Griinwald  8  have  also  investigated  the 
interrelationship  of  the  spectra  of  various  elements,  but  Ames' 
work  alone  has  proved  to  be  of  permanent  value.  He 
measured  the  wave-length  of  the  triplets  in  the  spectra  of 
zinc  and  cadmium,  and  calculated  the  differences  in  the 
number  of  waves  between  the  third  lines  of  the  triplets;  they 
decrease  from  triplet  to  triplet,  are  nearly  identical  for  each 
element,  and  prove  the  lines  to  be  true  homologues.  In  the 
more  strongly  nebulous  series  the  values  for  zinc  are  581,  263, 
141,  84,  and  for  cadmium  587,  264,  and  84. 

The  investigations  of  Kayser  and  Runge,  and  of  Rydberg 
have  thrown  most  light  on  the  relation  between  the  spectra 
of  different  elements.  Their  method  consists  in  a  combina- 
tion of  calculation  and  observation,  their  own  exact  remeas- 
urements  of  spectrum-lines  being  utilized  by  the  first  two 
observers.  The  relationship  of  the  spectra  of  different  ele- 
ments follows  from  the  law  already  stated  which  expresses 
the  connection  between  the  lines  of  a  single  element.  In 
spectra  of  similar  structure  the  homologous  lines  are  those 
with  identical  ordinal  numbers.  The  work  hitherto  completed 
shows  that  the  spectra  fall  into  the  same  groups  as  the  ele- 
ments. In  the  case  of  the  first  three  groups  of  the  periodic 

C.  r.  (1871)  72,  620.    . 

Ibid. 

Wien.  Ber.  (1878)  78,  767;  (1880)  82  [2]. 

Jour.  Chem.  Soc.  London  (1882)  84;  1883,  390. 

P.  M.  (1890)  [5]  30,  33. 

Astr.  Nachr.  (1887)  117.  Wien.  Ber.  (1887)  96  [2];  (1889)  97  [2]; 
(1890)  98  [2].  Wien.  Anz.  1890.  Comp.  also  Ames,  N.  (1888)  38.  Kayser, 
Chem.  Ztg.  (1889)  13;  (1890)  14.  Runge,  P.  M.  (1890)  [5]  30.  Grim- 
wald,  Chem.  Ztg.  (1890)  14. 


SPECTRUM  ANALYSIS. 


s->m  's-  /a  "i    s-  K  n  I  -S-'N  : 


SPECTRA.  91 

system  the   subdivisions  are   also  well   marked,  so   that  the 
following  classification  may  be  made: 

1.  Lithium,  sodium,  potassium,  rubidium,  caesium. 

2.  Copper,  silver. 

3.  Magnesium,  calcium,  strontium. 

4.  Zinc,  cadmium,  mercury. 

5.  Aluminium,  indium,  thallium. 

In  each  of  the  above  groups  the  spectrum  approaches  the 
red  as  the  atomic  weight  increases,  but  in  passing  from  group 
to  group  it  approximates  towards  the  violet.  The  systematic 
representation  of  these  spectra  as  given  by  Kayser  and  Runge 
is  shown  in  Fig.  40;  the  values  given  are  the  number  of 
vibrations,  and,  for  the  sake  of  clearness,  only  the  first  lines 
of  pairs  and  triplets  which  have  been  actually  observed 
are  shown ;  the  figures  opposite  to  the  lines  are  their  ordinal 
numbers. 

The  interrelationship  of  spectra  and  atomic  weights  has 
been  already  referred  to:  it  may  be  briefly  expressed  by 
saying  that  the  breadth  of  pairs  and  triplets,  measured  by  the 
difference  in  the  number  of  their  waves,  is  approximately 
proportional  to  the  square  of  the  atomic  weight. 


CHAPTER  VII. 
SPECTRA   OF   THE   ELEMENTS. 

AN  accurate  knowledge  of  spectra  is  of  the  greatest  im- 
portance for  any  application  of  spectrum  analysis ;  the  standard 
of  measurement  is  the  wave-length  in  air,  at  medium  tern- 

o 

peratures,  under  a  pressure  of  760  mm.  expressed  in  Ang- 
strom's units  (A)  or  tenths  (/*/*).  Until  recently  all  observa- 
tions were  based  on  Angstrom's  wave-length  determinations, 
and  on  his  drawings  of  the  solar  spectrum  (Spectra  normal  du 
Soleil1);  this  scale  was  universally  employed  during  twenty 
years,  but  after  Angstrom's  death  it  was  shown  by  Thalen2 
to  be  inaccurate  in  consequence  of  Angstrom  having  used  a 
reputed  metre  measuring-rod  less  than  one  metre  in  length. 
New  determinations  of  absolute  wave-lengths  have  been 
subsequently  made  by  Miiller  and  Kempf,3  Kurlbaum,4 
Peirce,5  and  Bell;6  of  these  the  values  for  the  Z^-line  of 
Peirce  and  of  Bell  agree  exactly,  and  that  of  Muller  and 
Kempf  very  closely;  the  latter  is  used  as  the  basis  of  the 
Potsdam  system.  Since  the  relative  values  are  often  of 
greater  importance  for  spectroscopic  purposes  than  the  abso- 
lute ones,  Rowland7  combined  the  various  numbers  as  shown 
below,  and  employed  the  mean  value  as  the  foundation  of  his 

1  Recherches  sur  le  spectre  du  soleil  (Upsala,  1868). 

2  Sur  le  spectre  de  fer.  N.  A.  S.  U.  1884  [3]. 

3  Publicat.  des  Astrophysikal.  Obs.  zu  Potsdam  (1886),  5. 

4  W.  A.  (1888)  33,  159,  381. 

5  Sillim.  Journ.  [3]  18,  51. 

6  P.  M.  (1888)  [5]  25,  245,  350. 

7  Astronomy  and  Astrophysics  (1893),  12,  321.     P.  M.  (1894)  [5]  36,  49. 
A  list  of  the  standard  wave-lengths  is  given  in  the  chapter  on   the  solar 
spectrum  together  with  references  to  Rowland's  latest  publications  on  the 
subject. 

92 


SPECTRA    OF   THE  ELEMENTS. 


93 


solar  atlas,  and  standard  wave-lengths  obtained  by  the  coin- 
cidence method;  as  this  admits  of  a  degree  of  exactitude 
(o.oiA)  otherwise  unattainable,  all  recent  measurements  have 
been  based  on  his  scale. 


Relative 
Weights. 

Observer. 

A- 

I 

Angstrom    corrected 

by  Thalen  

5805.81 

2 

Miiller  and  Kempf  .  . 

5806.25 

2 

58o5  .  QO 

5806    2O 

IO 

Bell  

5806.  2O 

5806    156 

The  wave-lengths  of  the  spectrum  lines  given  in  the  suc- 
ceeding pages  are  all  based  on  Rowland's  system ;  this  has 
entailed  a  recalculation,  by  the  use  of  Watts'  tables,1  of  all 
measurements  published  before  1889,  and  also  of  certain 
others.  The  object  of  the  tables  was  to  exhibit  the  relation- 
ship between  Angstrom's  and  Cornu's  solar  atlases  and 
Rowland's.  To  reduce  Angstrom's  scale  to  his  own  system 
of  wave-lengths  Rowland  multiplies  the  values  by  the  factor 
1. 00016. 

Such  recalculations  are  open  to  objections,  but  these 
are  overruled  by  the  great  inconvenience  of  wave-lengths 
determined  by  two  different  scales,  particularly  when  they 
refer  to  the  same  element;  moreover  the  table  permits 
of  the  revised  values  being  reconverted  into  the  original 
ones.  The  accuracy  of  the  older  measurements  should  not 
be  overrated,  it  falls  far  short  of  that  attainable  by  the 
use  of  the  grating  and  photographic  appliances,  such  as 
have  been  used  by  Kayser  and  Runge,  Liveing  and  Dewar, 
Hartley  and  Adeney,  Hasselberg,  Ames,  Trowbridge,  and 
others.  Most  of  the  older  measurements,  with  the  refer- 
ences, have  been  taken  from  Watts'  '*  Index  of  Spectra,"* 

1  B.  A.  R.  (1890).     (London,  1891),  p.  224. 

*  Manchester,  1889.     Continuations  are  given  in  the  B.  A.  R. 


94 


SPE CTK  UM  A  NA  L  YS1S. 


TABLE  FOR  THE  REDUCTION  OF  ANGSTROM'S  AND   CORNU'S  WAVE-LENGTHS 
TO  ROWLAND'S  VALUES,  DERIVED  FROM  THE  UNIT  D\  —  5896.156. 


Wave-length. 

Corr. 

Wave-length. 

Corr. 

Above 

6930 

+  1-7 

From  4970 

to  4935 

4-1.0 

From 

6930  to 

6880 

1.6 

"   4935 

"  4865 

0.9 

" 

6880  " 

6820 

1.5 

"   4865 

"  4740 

I.O 

«« 

6820  " 

6800 

1.4 

"   4740 

44  4650 

0.9 

" 

6800  " 

6765 

1-3 

"   4650 

44  4470 

0.8 

4 

6765  " 

6720 

1.2 

"   4470 

44  438o 

0.7 

" 

6720  " 

6660 

I.I 

"   438o 

"  4170 

0.6 

" 

6660  " 

6230 

I.O 

"   4170 

"  4130 

0.7 

44 

6230  " 

6180 

0.9 

"   4130 

"  4100 

0.8 

44 

6180  " 

6i55 

I.O 

44   4100 

'  '  4060 

0.7 

n 

6i55  " 

6135 

I.I 

"   4060 

4  '  4040 

0.6 

«• 

6i35  " 

6130 

I.O 

44   4040 

"  3850 

0.7 

44 

6130  " 

6110 

0.9 

"   3850 

'  3730 

0.6 

" 

6110  " 

6080 

1.0 

44   3730 

"  3720 

0-5 

«4 

6080  " 

6060 

1.  1 

"   3720 

'  '  3660 

0.4 

44 

6060  " 

6000 

I.O 

"   3660 

14  3640 

0.8 

44 

6000  '  ' 

5970 

0.9 

"   3640 

44  3620 

0.6 

1C 

5970  " 

5810 

I.O 

••   3620 

"  3530 

0.8 

" 

5810  •• 

578o 

0.9 

"   3530 

4  348o 

0.6 

" 

578o  " 

5610 

I.O 

44   348o 

'  3470 

0.8 

44 

5610  " 

5540 

I.I 

44   3470 

"  3440 

0.7 

II 

5540  " 

5485 

I.O 

41   3440 

"  3420 

i.i 

14 

5485  " 

5435 

0.9 

3420 

"  336o 

i-7 

II 

5435  " 

5350 

I.O 

44   3360 

44  3330 

2.5 

44 

5350  " 

5335 

0.9 

44   3330 

44  3290 

2.2 

14 

5335  " 

5325 

I.O 

41   3290 

44  3280 

2.O 

" 

5325  " 

5300 

0.9 

44   3280 

44  3240 

1.9 

4< 

5300  " 

5175 

I.O 

44   3240 

"  3220 

1.8 

«  I 

5175  " 

5150 

0.9 

44   3220 

44  3190 

0.8 

11 

5150  " 

4990 

0.8 

44   3190 

44  3160 

0.4 

4990  " 

4970 

0.9 

which  gives  a  fairly  complete  list  of  the  measurements  of  line- 
spectra  made  before  its  appearance.  In  the  following  pages 
the  lines  of  each  spectrum  or  portion  of  a  spectrum  are  all 
from  one  series  of  measurements,  and  that  the  newest  or 
most  trustwothy;  only  the  brighter  lines  have  been  included. 


SPECTRA    OF   THE   ELEMENTS.  95 

in  general  those  between  I  and  3  on  the  German  scale  of 
brightness,  in  which  the  brightest  is  I  and  the  faintest  6.  In 
the  English  scale  the  brightness  increases  from  I  to  10,  so 
that  the  lines  included  are  those  between  6  and  10,  but  where 
the  fainter  lines  are  characteristic  they  have  also  been  given. 
The  lines  are  not  provided  with  intensity-scale  numbers 
which  are  only  of  value  in  the  case  of  closely  adjacent  lines, 
whilst  their  assignment  is  always  somewhat  arbitrary,  but  in 
order  to.  facilitate  orientation  the  specially  bright  lines  have 
been  printed  in  bolder  type.  The  arrangement  of  the  tables 
follows  the  ordinary  plan:  double  or  triple  lines  are  enclosed 
in  parentheses;  bands  are  indicated  by  b,  those  sharply 
bounded  at  the  red  end  and  shading  gradually  towards  the 
violet  are  distinguished  by  br,  those  showing  the  opposite 
behavior  by  bv.  Lines  which  are  usually  designated  by  a 
number  or  letter,  such  as  the  Z^-line,  have  these  enclosed  in 
brackets,  and  prefixed  to  the  wave-length;  measurements 
are  given  to  as  many  places  of  decimals  as  are  required  by 
the  accuracy  of  the  observation.  Listing's 1  scale  is  used 
for  the  classification  of  the  lines  according  to  color;  it  runs 
as  follows: 

....  to  7230  infra-red.  5850  to  5750  yellow.  454°  to  4240  indigo. 
7230  "  6470  red.  5750  "  4920  green.  4240  "  3970  violet. 
6470  "  5850  orange.  4920  "  4550  blue.  3970  " ultra-violet. 

The  delicacy  of  spectrum  reactions  has  been  determined 
by  Kirchhoff  and  Bunsen  for  certain  flame-spectra,  and  by 
Cappel  for  a  series  of  spark-spectra;  the  number  in  the  table 
below  gives  that  fraction  of  a  milligram  of  pure  substance 
that  could  be  detected. 

KIRCHHOFF  AND  BUNSEN.S 

Barium  chlorate 1000                 Potassium  chlorate 1000 

Caesium  chloride 20000                 Rubidium  chloride 5000 

Calcium  chloride 16666                 Sodium  chlorate 3009000 

Lithium  chlorate nun                 Strontium  chloride 16666 

1  P.  A.  (1868)  131,  564.  2  Ibid.  (1860)  110,  161. 


96 


SPECTRUM  ANALYSIS. 


Cappel's1  results  are  as  follows: 


Bismuth  •  • 

7OOOO 

Indium     .  .  . 

9OOOO 

Potassium 

iSoOO 

Iron        .  . 

26OOO 

4OOO 

Lead 

2OOOO 

Calcium.  .  .  . 
Chromium.  . 
Cobalt  . 

I  0000000 

4000000 

ISOOO 

Lithium.  .  .  . 
Magnesium. 
Manganese. 

4OOOOOOO 
5OOOOO 
200000 

Strontium  .. 
Thallium.  .  . 
Tin  .. 

I  00000000 

80000000 
i7orx> 

Copper 20000         Mercury...          10000 


Zinc, 


600000- 


ALUMINIUM. 

The  visible  portion  of  the  spark-spectrum  of  aluminium 
has  been  investigated  by  Kirchhoff,2  Thalen,3  and  Lecoq  de 
Boisbaudran,4  and  the  ultra-violet  region  by  Hartley  and 
Adeney,  and  Cornu  ;5  the  latter  gave  a  graphic  representation 
of  the  lines  of  shortest  wave-length,  together  with  a  formula 
from  which  Julius 'was  enabled  to  calculate  the  wave-length. 
The  arc-spectrum  has  been  measured  by  Liveing  and  Dewar,7 
and  more  recently  by  Kayser  and  Runge,8  who  were  unable 
to  detect  a  single  line  in  the  visible  spectrum,  although  the 
bands  of  alumina  were  always  visible.  These  have  been 
investigated  by  Hasselberg,  and  are  given  in  a  separate  table 
below. 

Arc  and  spark  spectra: 


5723.5* 

5696.5* 

5057.4* 

4662.9* 

3961.68 

3944  26 

3092.95 

3092.84 

3082.27 

3066.28 

3064.42 

3060.04 

3057.26 

3054-81 

3050.19 

2660.49 

2652.56 

2575.20 

2568.08 

23/8.52 

2373.23 

2367.16 

2269.20 

2263.52 

2210.15 

2204.73 

2174.13 

2168.87 

2150.69 

2145-48 

1989.90 

1935.25 

1862.20 

1854.09 

1  P.  A.  (1870)  139,  628. 

2  A.  B.  A.  1861. 

3  N.  A.  S.  U.  (1868)  [3]  6. 

4  Spectres  lumineux  (Paris,  1874). 

6  Spectre  normal  du  Soleil  (Paris,  1881).     C.  r.  (1885)  100,  1181. 

6  Naturk.  Verh.  d.  Akad.  v.  Wetensch.  Amsterdam  (1888),  26. 

7  P.  R.  S.  28,  367.     P.  T.  (1883)  174,  220. 

8  A.  B.  A.  1892.     Runge,  W.  A.  (1895)  55,  44.     See   also  E.  Becquerel, 
C.  r.  96,  1218;  97,  72. 

*  Visible  only  in  the  spark  spectrum.     (Thalen.) 


SPECTRA    OF   THE   ELEMENTS. 


97 


ALUMINIUM    OXIDE. 


Arc-spectrum : 


Group  5210  —  5079: 

5162.05 

5156. 

45 

5155.42 

5147' 

93 

5143.27 

5I43-08 

5123. 

79 

(5123.57 

5123.47) 

5102.84 

5102 

.32 

5079.52 

Group  5041  —  4842: 

49I4-35 

4909. 

55 

4908.21 

4906.71 

4906.52 

4906.07 

49°5- 

22 

4905.04 

4904. 

84 

4903.72 

4903. 

54 

4899.16 

4895.20 

4895. 

00 

4892.32 

4890. 

44 

4888.57 

4888.41 

4887.79 

4886.08 

4885. 

87 

4883.45 

4882. 

43 

4882.24 

4881. 

25 

4880.07 

4879- 

9i 

4878. 

90 

4878.79 

4877. 

75 

4876.64 

4876. 

56 

4875.46 

4873. 

50 

4873. 

35 

4872.46 

4872. 

29 

4871.48 

4870.46 

4869.45 

4868. 

42 

4867. 

48 

4866.54 

4863. 

09 

4862.77 

4842.44 

Group  4842  —  4648: 

4810.16 

4809. 

80 

4766.75 

4766. 

53 

4760.32 

4752. 

53 

4752. 

27 

4749-19 

(4745- 

17 

4744.95) 

4742. 

56 

(4736.08 

4735- 

94) 

4727. 

40 

(4719.41 

4719. 

29) 

4715.45 

4711. 

98 

4711.81 

(4707. 

53 

4707. 

26) 

(4706.26 

4706. 

17) 

(4706.01 

4705. 

89) 

4699.00 

4697. 

90 

(4695. 

30 

4694.78) 

4689. 

77 

4672.15 

4658. 

68 

4655.34 

4648. 

14 

Group  4648  —  4471. 

4593-97 

4570.44 

4557.84 

4547- 

33 

4543-23 

4537. 

69 

4534- 

24 

(4523.45 

4522. 

86) 

4516.54 

45II- 

38 

4494.22 

4478. 

64 

4470. 

63 

ANTIMONY. 

The  spark-spectrum  is  obtained  either  by  the  use  of  the 
metal  or  of  a  concentrated  solution  of  the  chloride;  it  has 
been  measured  by  Kirchhoff,8  Huggins,3  Thalen,4  and  Hartley 
and  Adeney.6  The  arc-spectrum,  which  differs  from  that  of 
the  spark,  has  been  investigated  by  Liveing  and  Dewar,8  and 
the  portion  commencing  at  A  =  643;^  by  Kayser  and  Runge.7 

1  Hasselberg,  K.  Svenska  Vetensk.  Akad.  Handl.  (1892)  24,  No.  15. 
Lecoq  de  Boisbaudran.  Spectres  lumineux  (Paris,  1874).  Thalen,  Upsal. 
Universit.  Arsskrift.  1866.  Lockyer,  P.  T.  163,  658. 

A.  B.  A.  1861. 

P.  T.  (1864)  154,  139. 

N.  A.  S.  U.  (1868)  [3]  6. 

P.  T.  (1884)  175,  126. 

Ibid.  (1883)  174,  221. 

A.  B.  A.  1893.  Also  Lockyer,  P.  T.  (1873)  163,  369.  Lecoq  de  Bois- 
baudran, Spectres  lumineux  (Paris,  1874). 


98  SPECTR UM  ANA L  YSIS. 

In  the  visible  portion  of  the  field  the  lines  are  feeble  and  ill- 
defined,  and  are  not  present  in  the  spark-spectrum,  the  lines 
of  which  are  absent  from  the  arc-spectrum.  According  to 
Lockyer  and  Roberts  '  antimony  vapor  produces  a  continuous 
absorption-spectrum  in  the  blue. 
Arc  and  spark  spectra: 


6302.8* 
5568.25 

3598.6! 
33389t 

2QI3.lt 
2670.73 

2506.9! 
2262.55 

6129.7* 

4949-7* 
3566.8! 

3305-4t 
2890.7! 
2652.70 
2445-59 
2179-33 

6079.2* 

4878.6* 

3559-9t 
3267.60 
2878.01 
2631.6! 
2383.7^ 
2175.99 

6004.7* 

4592.4* 
3505.2f 
3232.61 
2790.0! 
2616.7! 
2373-78 
2098.47 

5910.1* 
4352.6* 

3499-  if 
3029.91 
2770.04 
2612.40 
2360.60 
2068.54 

5894.6* 
4265.6* 

3474-7! 
2980.2! 
2719.00 
2598.16 
2311.60 

5639-1* 
3739-6! 
3427.0! 
2965.6! 
2682.86 
2528.60 
2306.56 

ARGON. 

Argon  was  isolated  from  the  atmosphere  in  1894  by 
Rayleigh  and  Ramsay.2  The  pure  gas,  in  a  Geissler  tube, 
exhibits  several  lineal  spectra  depending  on  the  pressure  in 
the  tube  and  on  the  nature  of  the  electric  discharge.  Crookes  3 
discovered  two  of  these,  and  from  the  predominant  color  of 
their  light  termed  them  the  red  and  the  blue  spectrum 
respectively.  Eder  and  Valenta4  have  observed  a  third 
spectrum,  which  they  term  the  white.  It  is  produced  by  the 
use  of  very  large  condensers  in  conjunction  with  a  powerful 
induction-coil  and  a  strong  current.  In  these  circumstances, 
under  a  pressure  of  15-20  mm.,  white  light  is  emitted  from 
the  capillary.  Spectroscopically  the  light  is  peculiar;  the 
majority  of  the  lines  become  widened,  and  few  remain  sharp, 
many  coincide  with  lines  in  the  blue  and  red  spectra,  but 

1  P.  R.  S.  (1875)  23,  344. 

2  P.  T.  (1895)  186,  221. 

3  C.  N.  (1895)  72,  66,  99. 

4  Sitzungsbericht  d.  Wiener  Akad.  Mathem.-Naturw.  (1895)  404.  Denk- 
schr.  d.  Wiener  Akad.  (1896)  64. 


*  Visible  only  in  the  spark-spectrum.     (Thalen.) 

!  Visible  only  in  the  spark-spectrum.     (Hartley  and  Adeney.) 


SPECTRA    OF   THE   ELEMENTS.  99 

o 

certain  groups  are  displaced  from  0.5-1  Angstrom  towards 
the  red.  At  present  Eder  and  Valenta  are  unable  to  suggest 
the  cause  of  this  partial  displacement,  but  it  appears  to  be 
connected  with  the  pressure  and  temperature  of  the  gas,  and 
with  the  nature  of  the  electric  discharge.  There  is  still  some 
doubt  as  to  whether  argon  is  an  element  or  a  mixture  of  two. 
Dewar,  and  subsequently  Berthelot  have  suggested  that  it  is 
an  allotropic  modification  of  nitrogen,  but  later  work  does  not 
lend  confirmation  to  this  view.  The  gas  obtained  from 
cleveite,  which  was  formerly  supposed  to  be  nitrogen,  has 
been  shown  by  Ramsay  to  exhibit  all  the  lines  of  atmospheric 
argon  together  with  several  others  including  the  Z>3-line  °f 
helium ;  but  atmospheric  argon  contains  at  least  three  bright 
lines  in  the  violet  which  are  not  shown  by  the  gas  from 
cleveite;  hence  Ramsay  concludes  that  atmospheric  argon  is 
probably  a  mixture.  Berthelot l  obtained  a  fluorescent  spec- 
trum by  the  action  of  a  moderately  strong  induction-current 
on  a  mixture  of  argon,  benzene  vapor,  and  mercury  in  a 
Geissler  tube;  the  spectrum  differs  from  that  given  by  any 
other  gas,  and  the  yellow  and  green  rays  were  perfectly 
visible  in  the  spectroscope  in  full  daylight.  He  considers 
that  the  spectrum  is  that  of  a  compound  of  argon  and  mercury 
with  the  constituents  of  benzene,  but  Dorn  and  Erdmann  2 
found  that  some  of  the  lines  were  those  of  mercury  and 
nitrogen.  Eder  and  Valenta3  have  photographed  the  argon 
spectrum  between  A.  =  5060  and  332O/*/-*,  using  a  powerful 
concave  grating,  and  Kayser4  has  published  a  preliminary  list 
of  the  lines  in  the  blue  spectrum,  the  gas  being  obtained  from 
the  atmosphere;  the  lines  observed  are  not  given  in  Rowland's 
Atlas  and  reproductions  of  the  Fraunhofer  lines. 


1  C.  r.  (1895)  120,  662,  797,  1049,  1386;  (1897)  124,~  113. 

2  Lieb.  Ann.  (1895)  287,  230. 

3  Wiener  Akadem.  Anzeiger  (1895),  No.  21. 

4  C.  N.  (1895)  72,  99.     Sitzungsber.  d.  ,Ber,k  Akad..(i896)  24.     See  also 
Newall,  C.  N.  71,  115. 


100 


SPECTR UM  ANAL  YSIS. 


Trowbridge  and  Richards '  find  that  the  oscillatory  dis- 
charge of  the  condenser  is  an  important  factor  in  producing 
the  blue  spectrum  of  argon.  The  pure  red  spectrum  is 
obtained  if  the  tube  is  connected  with  the  terminals  of  an 
electric  machine;  but  if  the  spark-gap  is  interposed,  the  spec- 
trum changes  at  once  to  blue. 

Red  spectrum: 


7723.4 

7635.6 

7515-4 

7383-9 

7066.6 

6964.8 

6415.2 

6031.5 

5739.87 

5651.03 

5607.44 

5597.89 

5572.87 

5559-02 

5506.42 

5496.16 

5451.95 

5421.68 

5221.65 

5187.47 

5162.59 

4888.21 

4702.40 

4628.60 

4596.30 

4522.49 

4510.90 

4345.27 

4335.42 

4333-65 

4300.18 

4272.29 

4266.44 

4259.50 

4251.27 

4200.75 

4198.40 

(4191.02 

4190.85) 

4182.03 

4164.36 

4158.65 

4152.97 

4054.65 

4046.04 

4044.52 

3949.08 

3947-75 

3894.78 

3834-83 

3781.07 

3680.30 

3678.43 

3649.99 

3634.64 

3632.82 

3606.69 

3588.64 

3567.88 

3564.54 

3563.50 

3554.48 

3461.23 

3394.03 

3034.7 

3021.9 

2967.3 

2614.6 

2516.3 

2478.65 

Blue  spectrum: 

6644.2 

6059.5 

6043.0 

6031.5 

5651.03 

5607.44 

5559  02 

5496.16 

5287.24 

5166.03 

5145.57 

5142.20 

5062.35 

5017.46 

5009.63 

4965.38 

4933-49 

4880.14 

4866.14 

4847.94 

4806.17 

4765.04 

4736.03 

4658.04 

4637.35 

4609.73 

4590.05 

4579-53 

4545.26 

4503.15 

4481.99 

4426.16 

4401.19 

4400.25 

4379-79 

4371.46 

4370.92 

4352.40 

4348.11 

433L3I 

4283.03 

4277.65 

4266.44 

4237.34 

4228.27 

4222.76 

4182.97* 

4179.45 

417^.58 

4175-25* 

4174.20* 

4172.95* 

4172.05* 

4156.30 

4I3L95 

4113.04 

4104.10 

4082.59 

4079.80 

4076.85 

4072.58 

4072.  18 

4053-12 

4043.04 

4038.99 

4035.58 

4033.99 

4013.97 

3992.17 

3979-57 

3974.70 

3946.20 

3944.50 

3932.71 

393L32 

3928.78 

3925.93 

3914.93 

3911.69 

3907.80 

3892.15 

3891.53 

3880.46 

3875.40 

3872.26 

3868.68 

3850.70 

3845.51 

3841-63 

3830.58 

3826.92 

3809.58 

3808.72 

3803.38 

3799-65 

3795.56* 

3786.60 

3781.07 

3766.30 

3765.48 

3763-76 

3753.6o 

3738.04 

3734-70 

3729.52 

3720.61 

3718.39 

3717.36 

3660  70 

3656.26 

3655.52 

3651.04 

3640.00 

3637.25 

3622.31 

358864 

3582.54 

3581.82 

3576.80 

3565-20 

3561.20 

3559.69 

3548.69 

3546.03 

3545.78 

3535-53 

3522.14 

3521.46 

3520.15 

35I4.53 

3509.93 

3491.71 

3480.69 

3478.42 

3476.96 

3464.33 

3454-30 

3421.80 

3391-86* 

3388.65 

1  Amer.  Jour.  Sci.  1897  [4]  3, 

15.     P.  M. 

43,  77- 

See  also 

Friedlander, 

Zeit.  f.  phys. 

Chem.  (1896)  19,  662. 

*  Visible  only  by  the  use  of  powerful  condensers,   otherwise   absent 
from  the  normal  blue  spectrum. 


SPECTRA    OF   THE  ELEMENTS.  1OI 

3376.61      3351-10      3307-37      3301.97      3293-82      3285.91      3281.83 


3263.71 

3204.49 

3181.26 

3169.88 

3161.64 

3139.26 

3093.57 

3029.10 

2979-35 

2955.67 

2943.17 

2924.92 

2896.97 

2891.87 

2866.0 

2806.3 

2769.7 

2753-9 

2744-88 

2732.67 

2708.40 

2647.6 

2562.3 

2544.8 

2534.8 

2516.8 

2515-6 

2500.4 

2491.0 

2480.9 

2479.2 

2454-5 

2438.8 

2415.7 

2395-7 

2364.2 

2350.6 

2344-4 

2337.8 

233L7 

2316.5 

2314.0 

2309.4 

2282.6 

2252.4 

2243.7 

2234-7 

2219.9 

2175.6 

2171.5 

2165.8 

2130.6 

2050.5 

White 

spectrum 

: 

5306.04 

5287.24 

5166.03 

5145-57 

5142.20 

5062.35 

5017.46 

5009.63 

4972.40 

4965.38 

4933-49 

4888.88 

4880.14 

4867.72 

4847.94 

4806.17 

4765.04 

4736.03 

4727-00 

4658.04 

4609.75 

4590.04 

4579.53 

4545.26 

4481.99 

4430.35 

4426.16 

4401.19 

4400.25 

4379-79 

4371.46 

4370.92 

4352.40 

4348.11 

4332.20 

4331-31 

4278.02 

4266.44 

4228.27 

4104.93 

4072.3 

4013.97 

3933-40 

3928.78 

3892  15 

3869.50 

3850.70 

3827-67 

3781.58 

3766.21 

3729.52 

3589.11 

3582.79 

3577-27 

3561.50 

3560.15 

3546.58 

3514.98 

3510.26 

349I-7I 

3477.38 

3388.94 

3377.J8 

335i.8o 

3294.58 

ARSENIC. 

The  spark-spectrum  of  arsenic  is  obtained  by  the  use  of 
the  vapor  of  the  element,  or  of  the  chloride  contained  in  a 
Geissler  tube.  The  arc-spectrum  differs  from  that  of  the 
spark,  and  exhibits  no  lines  in  the  visible  field;  the  portion 
from  6ooyw//  onwards  has  been  photographed  by  Kayser  and 
Runge;'  between  3OO/f/u  and  2OO/^u  the  lines  are  numerous 
though  not  very  strong,  but  they  are  often  observed,  showing 
the  wide  distribution  of  arsenic,  and  its  frequent  occurrence 
as  an  impurity ;  indeed  the  lines  \  =  2349  and  2288,  which  are 
the  strongest,  are  rarely  absent  from  any  spectrum  of  a  carbon 
arc.  Lockyer2and  Ciamician  3  have  described  a  channelled 
absorption-spectrum. 

1  A.  B.  A.  1893. 

2  C.  r.  (1874)  78,  1790. 

a  Wien.  Ber.  76,  499;  78,  867;  82,425.  See  also  Thalen,  N.  A.  S.  U. 
(1868)  [3]  6.  Hartley  and  Adeney,  P.  T.  (1884)  175,  124.  Kirchhoff,  A.  B. 
A.  1861.  Huggins,  P.  T.  (1864)  154,  139.  Plucker  and  Hittorf,  P.  T.  155, 
i.  Ditte,  C.  r.  (1871)  73,  738.  Huntingdon,  Sillim.  Jour.  (1881)  22,  214. 


102  SPECTRUM  ANALYSIS. 

Arc  and  spark  spectra: 

6170.7*  6111.2*  5652.1*  5559-2*  5499-1*  5332-1*  4494-7! 

4467.0!  4459-4t  4431- 7t  4036.7t  3949.2!  393i-4t  3922.3! 

3825.1!  3785-0!  3119.69  3075.44  3057.7!  3053-0!  3032.96 

2991.11  2898.83  2860.54  2830.2!  2780.30  2745.09  2601.2! 

2528.3!  2526.4!  2492.98  2456.61  2437.30  2381.28  2370.85 

2369.75  234992  2288.19  2271.46  2228.77  2165.64  2157.1! 

2148.2!  21.14.21  2133.92  2113.14  2067.26  2009.31 

BARIUM. 

The  spark-spectrum  of  barium  has  been  investigated  by 
Kirchhoff,1  Huggins,2  Thalen,3  and  Lecoq  de  Boisbaudran;4 
the  arc-spectrum  by  Lockyer,5  Liveing  and  Dewar/  and, 
most  accurately,  by  Kayser  and  Runge,7  who  employed  the 
chloride  and  carbonate,  and  measured  162  lines.  Barium 
compounds  are  gradually  dissociated  in  a  hot  Bunsen  flame, 
and  all  exhibit  the  band-spectrum  of  the  oxide,  together  with 
line  A.  =  5 535. 69  of  the  metal.  Immediately  on  their  introduc- 
tion the  haloid  derivatives  produce  their  own  peculiar  fugitive 
spectra;  these  can  always  be  obtained  with  certainty  if  a  wire 
holding  ammonium  chloride  is  placed  in  the  flame  below  the 
specimen  of  barium  salt  under  examination.  For  prolonged 
experiments  hydrogen  chloride,  hydrogen  bromide,  or  iodine 
vapor  must  be  introduced  into  the  flame.  The  flame-spectra 
of  these  compounds  have  been  studied  by  Mitscherlich  8  and 
Lecoq  de  Boisbaudran. 

1  A.  B.  A.  1861. 

*  P.  T.  (1864)  154,  139. 

3  N.  A.  S.  U.  (1868)  [3]  6. 

4  Spectres  lumineux  (Paris,  1874). 

6  P.  T.  163,  369;   164.  806. 

*  Ibid.  (.1883).  174,  216. 

7  A.  B.  A.  1891. 

8  P.  A.  (1862)  116,  419;    (1863)  121,  459.      For  the  flame-spectrum   see 
also  Bunsen  and  Kirchhoff,  P.  A.  110,  161.   Bunsen,  P.  A.  (1875)  155,  366. 

*  Only  visible  in  the  spark-spectrum.     (Thalen.) 

!  Only  visible  in  the  spark-spectrum.     (Hartley  and  Adeney.) 


SPECTRA    OF   THE  ELEM. 


103 


Arc  and 

6497.07 
5853.91 

55I9-37 
4700.64 
4523.48 
3995-92  • 
3599-60 
277I-5I 

spark 

6141.93 

5826.50 
5424-82 
4691.74 
4506.11 
3993.60 

3544-94 
2634.91 

spectra  : 
6111.01 

5805.86 
5267.20 

4673.69 
4432.13 
3938.09 
3525.23 
2347.67 

6063. 
5800. 

4934. 

4579- 
4402. 

3935- 
3501. 

2335- 

33 
48 
24 
84 
75 
87 
29 

33 

6019.69 
5777.84 

4903." 
4574.08  • 

4350.49 
3910.04 
3357-00 
2304.32 

5971- 
5680. 
4900. 
4554. 
4283. 
3891. 
3071. 

94 
34 
13 
21 
27 
97 
7i 

5907-88 
•  5535.69 
4726.63 
4525.19 
4130.88 
3611.17 
2785.22 

Flame-spectra: 

Barium  bromide 5411  5359  (5305  5250)  5207  5150 

Barium  chloride —     5314  5243  (5206  5172)  5*37 

Barium  iodide 5608  5377 

Barium  oxide 6450  6298  (6240  6179  6109  6032) 

(5939  5868)  5825  (5769  5720  5648) 

5535.69*  5493  5347  5216  5090  4874- 

BERYLLIUM. 

The  whole  of  the  spectrum  of  this  element  has  not  hitherto 
been  thoroughly  investigated;  some  of  the  visible  lines  in  the 
spark-spectrum  have  been  measured  by  Thalen'  and  Kirch- 
hoff,8  and  Hartley*  has  observed  others  in  the  ultra-violet. 
Cornu  *  mentions  two  lines  in  the  arc-spectrum,  and  Crookes  * 
states  that,  when  caused  to  fluoresce  in  a  vacuum,  a  continu- 
ous blue  spectrum  is  produced.  Rowland  and  Tatnall 6  have 
recently  examined  the  arc-spectrum  between  \  =  2100—4600; 
the  lines  are  comparatively  feeble. 

Arc  and  spark  spectra: 

4572.869!   4489-4!   -  3905- 2f    3322. 3f    (3321.486    3321. 2i8> 
(3131.200    3130.556)   (2651.042    2650.414)   2649.8!   (2494.960 
2494.532)    2493. 6f     2478.1!     2348.698 


1  N.  A.  S.'U.  (1868)  [3]  6. 

-  A.  B.  A.  1861. 

*  J.  Chem.  Soc.  43,  316. 

4  Spectre  normal  du  soleil  (Paris,  1881). 

5  A.  c.  p.  [5]  23,  555.     See  also  Lockyer,  P. 
Wien.  Ber.xjY]  82,  425. 

6  Astrophys.  Jour.  (1895)  1,  16;  2,  185. 


R.  S.   27,  280.     Ciamiciaru 


*  Due  to  the  metal  itself. 


f  Spark  spectrum. 


104  SPECTRU'M  ANALYSIS. 


BISMUTH. 

The  spark  spectrum  is  obtained  by  the  use  of  bismuth 
electrodes,  and  has  been  measured  by  Huggins,1  Thalen,2  and 
Hartley  and  Adeney;3  the  arc-spectrum  by  Liveing  and 
Dewar,4  and  recently,  commencing  at  6i8/*ju,  by  Kayser  and 
Runge.5  The  spark-spectrum  exhibits  many  lines  that  are 
absent  from  that  of  the  arc.  Bismuth  salts,  moistened  with 
hydrochloric  acid,  produce  in  the  Bunsen  flame  a  fugitive 
band-spectrum  of  the  oxide.  The  spectra  of  the  compounds 
themselves  are  obtained  by  volatilizing  them  in  a  hydrogen 
flame.  They  have  been  drawn  by  Mitscherlich.6 

Arc  and  spark  spectra: 


6493.8* 
5271.1* 

4260.1* 

3654.7! 

2938.41 

2627.99 
2203.2 
2110.35 

6130.2* 
5209.0* 
(4122.01  ' 
3614.  6! 
2898.08 
2524.58 
2189.70 
2061.77 

6057- 
5144. 
4121. 
3596. 
2809. 
2515- 
2187. 

7* 
0* 

69) 
26 

74 

72 

4t 

5862. 
5124. 
4079. 
3ii5. 
2784. 
2489. 
2176. 

6* 
5* 

7t 

2f 

4t 

5 
70 

58I7.I* 
4993-9* 
3864.  4f 
3067.81 
2780.57 
2400.98 
2157.03 

5717.6* 
4722.72 

3793-3t 
3024.75 
2766.7! 
2276.64 
2152.98 

5552 
456o 
3757 
2993 
2730 
2230 
2134 

•44 
.9* 
,6f 
.46 
.61 
.70 
.38 

5451-0* 
4302.6* 
3695.7f 
2989.15 
2696.84 
2228.31 
2133.72 

BISMUTH    OXIDE. 
Flame-spectrum.     The  bands  are  measured  from  the  red. 

6383    6195    6040    5874    5718    5583    5445    5329    5221 

BORON. 

According  to  Kayser  and  Runge7  the  arc-spectrum  of  this 
element  consists  of  only  two  lines,   which,   together  with  a 

1  P.  T.  (1864)  p.  139. 

2  N.  A.  S.  U.  (1868)  [3]  6. 

3  P.  T.  (1884)  175,  130. 

4  Ibid.  (1883)  174,  222.     P.  R.  S.  29,  398. 

5  A.  B.  A.  1893. 

•  P.  A.  (1863)  121,  459.      See  also  Angstrom,  Ibid.  (1855)  94,  141.    Mas- 
cart,  Ann.  de  1'Ecole  normale  (1866),  4,  7.  E.  Becquerel,  C.  r.  96,  1218 ;  97,  72. 

'A.  B.  A.  1892. 

*  Visible  only  in  the  spark-spectrum.     (Thalen.) 

!  Visible  only  in  the  spark-spectrum.     (Hartley  and  Adeney.) 


SPECTRA    OF   THE  ELEMENTS.  10$ 

third,  have  also  been  observed  by  Hartley  '  in  the  spark- 
spectrum;  Eder  and  Valenta2  found,  however,  fourteen 
additional  lines,  the  majority  of  which  are  double,  and  con- 
firmed the  presence  of  four  that  had  been  detected  by 
Ciamician.3  Rowland  and  Tatnall4  have  recently  photo- 
graphed the  arc-spectrum  between  A,  =  2  100-4400.  Onl)r 
the  double  line  could  be  detected;  the  numerous  bands  are 
probably  due  to  some  compound,  such  as  boric  anhydride. 
Boric  acid  and  its  salts  produce  a  characteristic  band  spectrum 
in  the  Bunsen  flame. 

Arc  and  spark  spectra: 

3450.8*       (2497.821       2496.867)       2267.0!       2266.4! 

BORIC    ACID.5 

The  wave-length  is  measured  at  the  middle  of  the  bands. 
Flame-spectrum: 

6398   6211   6032   5808   5481   5440 
5193   4912   4722   4530 

BROMINE. 

Bromine  vapor  gives  a  line-spectrum  with  the  electric 
spark,8  but  the  measurements  of  it  are  only  approximate. 
Its  absorption-spectrum  at  the  ordinary  temperature  has  been 
accurately  investigated  by  Hasselberg;7  when  a  high  disper- 


1  P.  R.  S.  35,  301. 

2  Denkschr.  d.  Wien.  Akad.  (1893)  60,  307. 


3  Sitzber.  d.  Akad.  d.  Wiss.  zu  Wien.   [2]  82,  425.     See  also  Troost  and 
Hautefeuille,  C.  r.  (1871)  73,  620.     Salet,  A.  c.  p.  (1873)  [4]  28,  59. 

4  Astrophys.  Jour.  (1895)  1,  16. 

5  Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris,  1874).     Thalen,  Up- 
sal.  Universit.  Arsskrift.  1866.  Also  Salet  and  Eder,  and  Valenta,  as  above. 

6  Salet,  Spectroscopie  (Paris,  1888).     A.  c.  p.  [4]  28,  26.    Plucker,  P.  A. 
105,  527;  107,  87.      Plucker  and  Hittorf.  P.  T.    155,  i.     Ciamician,  Wien. 
Ber.  76  [2],  499;  77  [2],  839;  78  [2],  867. 

7  K.  Svensk.  Akad.  Handlingar.  (1891)  24,  No.  3.      Mem.  de  1'acad,  de 
St.  Petersb.  (1878)  26,  No.  4.     See  also  Daniell  and  Miller,  P.  A.  28,  386. 
Roscoe  and  Thorpe,  P.  T.  167,  209.     Moser,  P.  A.  160,  188. 

*  Visible  only  in  the  spark-spectrum.     (Hartley.) 

\  Visible  only  in  the  spark-spectrum.     (Eder  and  Valenta.) 


io6 


SPECTRUM  ANALYSIS. 


sion  is  employed  it  is  seen  to  consist  of  a  large  number  of 
fine  lines  grouped  into  bands. 

The  spectrum  obtained  with  a  continuous  discharge  differs 
from  that  produced  when  a  condenser  is  included  in  the 
circuit.1 

Spark-spectrum  of  bromine  vapor: 


7000*         6780 

*         6630* 

6583 

6559 

6546 

6353 

6148           5876 

5830 

5723 

55QO 

(5509 

5497 

5491)         (5450 

5423) 

(5327 

5305 

5240 

5184 

5166)         5060          4930 

(4816 

4788) 

4705 

4677 

4618           4366 

3980 

Absorption-spectrum  : 

Group 

6162  —  6142  : 

6158.09 

6I55.45 

6154.19 

6150.57 

6148 

.15 

Group 

6142  —  6122  : 

6125.12 

'6124.01 

Group 

6122  —  6103  : 

6117.61     b  (6116.47 

6115.67) 

6108  49 

Group 

6103  —  6079  : 

6083.20 

6082.50 

6080.  36 

6079.78 

Group 

6079  —  6066  : 

6077-85 

6069.61 

Group 

6066  —  6042  : 

6064.  50 

6055-95 

6055-76 

6055  22 

6054 

-78 

6054.25 

Group 

6042  —  6003  : 

6021.02 

6020.  i  5 

6018.40 

6017.73 

b  (6017 

.18 

6016.56) 

6013.46 

(6011,28 

6OII.O2) 

6008 

.26 

6008.03 

Group 

6003—5977  : 

5982.65 

5982.34 

5981.55 

5981.30 

5980.25 

Group 

5977—5949: 

5966.29 

5964-97 

5964.35 

5961.44 

596i. 

06 

5960.54 

5960.16 

5959  22 

5958.32 

Group 

5949—5935  : 

5942-73 

Group 

5935—5896: 

5929-33 

5924.62 

5924.23 

5924.00 

5906 

13 

5904-36 

5903-69 

5898.45 

Group 

5896—5862  : 

5869.91 

Group 

5862—5832: 

5854.95 

5846.34 

5844.78 

5843-44 

5838. 

81 

5838.16 

5837.59 

5836.95 

5836.41 

5832. 

43 

Group 

5832—5807: 

5828.60 

5812.41 

5812.18 

5809.57 

5808. 

87 

5808.15 

5807.95 

Group 

5807—5791: 

5802.82 

5802.26 

5800.93 

579S.I5 

5796 

Si 

5795.64 

5795-44 

Group 

5791—5763: 

5782.46 

5782.01 

5777-39 

5774-75 

5773- 

90 

5773-02 

577L29 

5765.71 

5765.03 

5764. 

42 

Group 

5763—5742: 

5760.33 

5748.57 

5747-55 

5744.46 

5742. 

54 

1  Trowbridge  and 

Richards, 

Amer.  Jour.  Sci.  (1897)  [4]  3, 

117.     P 

M 

43,  135. 

*  Inaccurate. 


SPECTRA    OF   THE  ELEMENTS. 


ID/ 


Group 

5742—5712: 

5739.81 

5730.97 

5738. 
5729. 

9i         5738. 
69    b(5727. 

ii 
63 

5737- 
5726. 

25 
98) 

5736. 
5726. 

49 

5725- 

79 

5725- 

54 

5715. 

38 

5712.44 

5712. 

18 

Group 

5712—5688: 

57H. 

38 

5702. 

53 

5701. 

83 

5698. 

62 

5697- 

29 

5693- 

89 

Group 

5688—5659: 

5678.02 

5676. 

93 

5667. 

97 

5667.20 

5666. 

46 

(5664. 

31 

5664. 

06) 

5663. 

52 

5659- 

37 

Group 

5659  —  5616  : 

5657.45 

5656. 

93 

5647.46 

5646. 

42 

5634. 

43 

5617- 

61 

Group 

5616—5587: 

5603.27 

5602. 

44 

5598. 

70 

5596. 

17 

5595- 

69 

5595. 

17 

5592.68 

Group 

5587—5555: 

5573 

-63 

5572.93 

5572.73 

b  (5570.47 

5569- 

90 

•';!;'v  •'          •'"*."' 

5569- 

56) 

(5566. 

75 

5566. 

33) 

5565. 

97 

5563- 

90 

o?: 

-^^\ 

5563- 

oo 

556i. 

35 

5550. 

44 

556o. 

16 

5559- 

86 

5557. 

42 

5556.93 

5556. 

39 

5556. 

03 

5555- 

86 

Group 

5555—5528: 

5542. 

08 

5530. 

65 

Group 

5528—5502  : 

(5506. 

88 

5506. 

36) 

5504. 

72 

5503. 

62 

Group 

5502—5477  : 

5500. 

58 

5498. 

60 

5496. 

41 

(5491.98 

5491- 

36) 

(5485. 

19 

5484- 

93) 

(5482. 

70 

5482. 

53) 

5482. 

17 

5479- 

32 

5478. 

96 

Group 

5477—5456: 

5468. 

94 

5467. 

24 

(5466. 

84 

5466. 

71) 

5464- 

96 

546i. 

81 

5460.74 

5460. 

19 

5457- 

15 

5456. 

89 

Group 

5456—5430: 

5455- 

62 

5442. 

86 

5439- 

75 

(5436.98 

5436. 

74) 

5432. 

25 

Group 

5430—5406  : 

5420.61 

5418. 

23 

54I7. 

50 

54I7. 

03 

54I5- 

96 

5414. 

76 

5413. 

91         5410.93 

5408. 

91 

Group 

5406—5372  : 

5390. 

90 

5389. 

92 

5377-93 

5375- 

92 

5372. 

3° 

5372. 

,11 

Group 

5372—5354: 

5356, 

49 

5353-So 

Group 

5354—5333: 

(5348. 

06 

5347- 

87) 

5342. 

38 

5341. 

82 

5340. 

92 

(5338. 

31 

5338. 

07) 

5333- 

ii 

Group 

5333—5317: 

(5329. 

60 

5329. 

30) 

(5319.77 

53I9- 

56) 

— 

Group 

5317—5289: 

(5290 

•47 

5290.21) 

Group 

5262—5243  : 

5256, 

.32 

5255.79 

5251- 

87 

5249- 

73 

5248. 

So 

5247- 

61 

5245. 

33 

Group 

5243—5215: 

5241. 

88 

5241. 

72 

5234- 

00 

5215- 

92 

Group 

5184—5159: 

5184. 

57 

5184. 

29 

5183.60 

5178. 

56 

5174- 

91 

5168. 

26 

5167.41 

5163.35 

5160. 

54 

CADMIUM. 

The  references  given  below  show  how  numerous  have  been 
the  investigations  of  the  cadmium-spectrum;  the  latest  are 
those  of  Kayser  and  Runge,1  who  occasionally  employed  the 

1  A.  B.  A.  1891. 


IO8  SPECTRUM  ANALYSIS. 

chloride,  but  usually  the  metal.  The  arc-spectrum  differs 
considerably  from  that  of  the  spark;  the  latter  exhibits  a  pair 
of  lines  of  the  highest  intensity  of  A  =  53/8.8  and  5338.3, 
which  are  absent  from  the  former,  and  the  same  applies  to 
90  lines  of1  inferior  brightness  between  X  =  4215  and  21 11 
which  have  been  measured  by  Hartley  and  Adeney.1  Cad- 
mium chloride  and  bromide  are  dissociated  in  the  Bunsen 
flame,  and  exhibit  the  lines  A  =  5086,  4800,  and  4678. 
Arc  and  spark  spectra : 

6467.3*  6438.8*  5378.8*  5338.3*  5154.85  5086.06f  4800.09f 

4678. 37f  4662.69  4413.23  361304  3610.66  3467.76  3466.33 

3403.74  3261.17  (3252.63  3133.29  3081.03)  2980.75  2880.88 

2763.99  2639.63  2601.99  2573.12  2329.35  2312.95  228810 

2267.53  2239.93  2194.67  2144.45 

CESIUM.2 

Bunsen  and  Kirchhoff  discovered  caesium  in  1861  by 
means  of  spectrum  analysis.  Its  salts  are  all  dissociated  in 
the  Bunsen  flame,  and  exhibit  the  lines  of  the  metal;  the 
more  prominent  ones  are  A  =  4555  and  4593  in  the  blue,  and 
A  =  6010  in  the  orange. 

Arc,  spark,  and  flame  spectra: 

6973.9      6723.6       6213.4      6010.6       5845.1       5664.0       5635.1 
4593-34      4555-44      3888.83      3876.73      3617.08      3611.84 

1  P.  T.  (1883)  175,  98.    See  also  Thalen,  N.  A.  S.  U.  (1868)  [3]  6.   Kirch- 
hoff,  A.   B.   A.   1861.     Mascart,    Annales   de    1'Ecole    hormale  (1866),  15. 
Lockyer,  P.  T.  (1873)  163,  369.     Cornu.  Journ.  de   Phys.   (1881)  10,  425. 
Liveing  and  Dewar,  P.  R.  S.  (1879)  29,  482.     P.  T.  (1888)  179,  231.   Ames, 
P.  M.  (1890)  [5]  30,  33.     Bell,  Am.  Journal  of  Sciences,  June,  1886. 

2  Kayser  and  Runge,  A.  B.  A.  1890.     Bunsen,  P.  A.  119,   i;    155,  366. 
Johnson  and  Allen,  P.  M.  [4]  25,  199.     Thalen,  N.  A.   S.    U.   (1868)  [3]  6. 
Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris,  1874).   Lockyer,  P.  R.  S. 
{1878)  27,  280.     Liveing  and  Dewar,  Ibid.  (1879)  28,  352. 


*  Only  visible  in  the  spark  spectrum.     (Thalen.) 

f  Visible   also  in    the    flame    spectrum   of   the    chloride    and    bromide. 
(Lecoq  de  Boisbaudran.) 


SPECTRA    OF   THE  ELEMENTS.  109 


CALCIUM. 

The  line-spectrum  of  calcium  has  been  measured  by 
Kirchhoff,1  Muggins,"  Thalen,3  Lecoq  de  Boisbaudran,4 
Lockyer,5  Cornu,6  Liveing  and  Dewar,7  and  more  recently  by 
Kayser  and  Runge,  8  who  employed  the  electric  arc  and 
calcium  chloride.  The  faint  bands  which  occasionally  appear 
in  the  yellow  and  red  when  the  arc  is  used  are  considered  by 
Lecoq  de  Boisbaudran  to  be  due  to  oxide.  Many  of  the 
calcium  lines  are  readily  produced,  and  are  therefore  always 
visible  when  carbon  electrodes  are  employed.  H.  Becquerel* 
observed  bands  from  A  =  8880-8830  and  from  A  =  8760-8580 
in  the  infra-red.  The  haloid  compounds  have  been  investi- 
gated by  Bunsen,  Mitscherlich, 10  and  Lecoq  de  Boisbaudran;1* 
in  the  Bunsert  flame  some  bands  peculiar  to  each  compound 
are  visible,  together  with  those  of  the  oxide  and  the  blue 
line,  A  =  4226.91,  of  the  metal.  The  oxide  bands  are  also- 
produced  if  the  flame  is  charged  with  hydrogen  chloride,, 
hydrogen  bromide,  hydrogen  iodide,  or  hydrogen  fluoride. 

Arc  and  spark  spectra: 

6499.85  6462.75  6439.36  6169.87  6162.46  6122.46  6102.99 

5867.94  5857.77  5603.06  5601.51  5598.68  5594.64  5590.30 

5588.98  5582.16  5513-07  5349.66  5270.45  5265.79  5264.46 

5262.48  5261.93  5189.05  5041-93  4878.34  4586.12  4581.66 

4578.82  4527-17  4456.08  4454.97  4435.86  4435.13  4425.61 

1  A.  B.  A.  1861. 

2  P.  T.  (1864)  154,  139. 

3  N.  A.  S.  U.  (1868)  [3]  6.     Spectre  du  fer  (Upsala,  1884). 

4  Spectres  lumineux  (Paris,  1874). 

5  P.  T.  (1874)  164,  809.     C.  r.   82,  660. 

6  Spectre  norm,  du  soleil  (Paris,  1881). 

I  P.  T.  (1882)  174,  187.      P.  R.  S.  28,  367,  475;  29,  398. 

*  A.  B.  A.  1891.  See  also  Mascart,  Ann.  de  1'ecole  normale  (1866),  15. 
Angstrom,  Recherches  sur  le  spectre  solaire  (Upsal,  1868).  Eder  and  Va- 
lenta,  Phot.  Corresp.  1893,  p.  59.  Rydberg,  W.  A.  (1894)  52,  119. 

9  C.  r.  94,  1218;  97,  72. 

10  P.  A.  121,  459 

II  Spectres  lumineux  (Paris,  1874). 


I  I O  SPECTR UM  ANAL  YSIS. 


4355- 

4i 

43i8, 

,80 

4307.91 

4302.68 

4299. 

14 

4289.51 

4283.16 

4226 

91* 

3973. 

,89 

3968.63 

3957.23 

3933. 

83 

3644.45 

3630.82 

3624. 

15 

3487. 

,76 

3361.92 

3350.22 

3344- 

49 

3I79.45 

3158.98 

239«. 

66 

2275 

.60 

CALCIUM    BROMIDE. 

Flame-spectrum : 

6267       6243       6103 

CALCIUM    CHLORIDE. 

Flame-spectrum: 

6266        (6203        6182)        (6069        6045)        5934 
5817         (5544         55i8)f 

CALCIUM    FLUORIDE. 
Flame-spectrum: 

6061       6027       5329       5302 

CALCIUM    OXIDE. 
Flame-specUupi : 

' \     *     0221         5996         (5544         5518) 
CARBON. 

This  element  htfs  been  more  frequently  investigated  than 
any  other;  its  spectra  are  extremely  complex,  but  it  is  now 
generally  acknowledged  to  exhibit  two,  a  line  and  a  band 
spectrum.  The  former  is  produced  by  the  passage  of  sparks 
from  a  Leyden  jar  through  carbon  dioxide  or  carbon  mon- 
oxide; its  visible  portion,  between  wave-length  3920-2266.5, 
has  been  measured  by  Angstrom  and  Thalen,1  and  the  ultra- 
violet part  by  Liveing  and  Dewar.a  The  band-spectrum  has 
also  been  termed  the  "  flame-spectrum,"  or  "  Swan's  spec- 
trum" ;  it  was  first  observed  by  Wollaston  3  in  1802,  and  then 

1  N.  A.  S.  U.  (1875)  [3]  9- 

2  P.  R.  S.  (1880)  30,  152,  494;  (1882)  33,  403;  (1883)  34,  123.   P.  T.  (1882) 
174,  187.     Also  Eder  and  Valenta,  Denkschr.  Wiener  Akad.  (1893)60. 

8  P.  T.  1802. 


*  Also  visible  in  the  Bunsen  flame.         f  Probably  due  to  the  oxide. 


SPECTRA    OF   THE   ELEMENTS.  Ill 

investigated  by  Swan1  from  1850  onwards.  In  common  with 
Angstrom,  Thalen,2  and  Liveing  and  Dewar,3  he  ascribed  it 
to  hydrocarbons,  but  the  last  workers,  together  with  Attfield,4 
Morren,5  and  Dibbits,8  subsequently  recognized  that  it  was 
due  to  carbon,  since  it  is  produced  by  the  combustion  of  pure 
cyanogen  in  dry  oxygen.  This  band-spectrum  consists  of  five 
complex  bands,  with  the  following  wave-lengths  according  to 
Angstiom  and  Thalen,  and  Watts:7 


i  or  orange  band.       y^ilow^anV         3  or  green  band.        4  or  blue  band.       5  or  indigo  band 
6187-5954  5633-5425  5164-5082  !  4736-4677  4331-4232 

The  three  medial  bands  have  been  recently  measured  by 
Fievez,8  and  the  green  one  by  Kayser  and  Runge;9  for  the 
others  there  are  only  the  old  observations  of  Watts,  Angstrom 
and  Thalen,  and  Piazzi-  Smyth  10  available.  In  addition  to 
the  above  bands  others  are  sometimes  observed  in  the  arc; 
they  occur  in  the  blue,  violet,  and  ultra-violet,  and  have  the 
following  wave-lengths: 

I  Band.  II  Band.  Ill  Band.,  IV  Band.  V  Band. 

4600-4500  4290-4150  3884-3856  3590-3550  3370-3350 

Their  existence  in  the  arc  is  doubted  by  Kayser  and 
Runge;  Liveing  and  Dewar  have  ascribed  them  to  cyanogen, 
whilst  Lockyer,11  H.  W.  Vogel,  and  others  regard  them  as  a 

1  P.  T.  E.  (1857)21,411. 

2  N.  A.  S.  U.  (1875)  9. 

3  P.  R.  S.  (1880)  30,  152,  4945(1882)  33,  403;  (1883)  34,  123.    P.  T.  (1882) 
174,  187. 

4  Ibid.  (1862)  152,  221.     P.  M.  (1875)  49,  106. 
B'A',c.  p.  (1865)  [4]  4,305. 

B  P.  A.  (1864)  122,  497. 

I  P.  M.  (1869)  [4]  38,  249;  45,  12;  (1874)  48,  369,  456;  (1875)  49,  104. 

8  Mem.  de  1'Acad.  roy.  de  Belgique  (1885),  47. 

9  A.  B.  A.  1889. 

10  Astr.  Obs.  Edinb.  (1871)  13,  58.     P.  M.  (1875)  [4]  49,  24;  (1879)  [s]  8, 
107.     P.  T.  E.  30,  93. 

II  P.  R.  S.  (1878)  28,  308;  (1880)  30,  335.     See  also  PlUcker,  P.  A,  (1858) 
105,  77;  (1859)  107,  533,  and  with  Hittorf,  P.  T.  155,  i.     Jahresber.  (1864) 
p.  no.     Van  der  Willigen,  P.  A.  (1859)  107,  473.     Huggins,   P.   T.   (1868) 


112  SPECTRUM  ANALYSIS. 

second  band-spectrum  of  carbon  produced  only  at  high  tem- 
peratures. Kayser  at  first  shared  this  view,  but  experiments 
made  in  conjunction  with  Runge  led  to  a  different  conclusion. 
A  strong  current  of  carbon  dioxide  was  directed  on  to  the 
arc,  whereupon  the  cyanogen  bands  became  fainter  and  dis- 
appeared. In  order  to  prove  that  this  was  not  due  to  a 
lowering  of  the  temperature  a  still  stronger  current  of  air  was 
substituted  for  the  carbon  dioxide:  the  bands  immediately 
increased  in  brightness  in  consequence  of  the  additional 
supply  of  nitrogen.  The  view  that  the  cyanogen  bands  are 
essentially  due  to  carbon  is  supported  by  their  occurrence  in 
comets,  and  in  the  solar  spectrum;  this  last  fact  was  long 
doubted,  but  was  established  by  Rowland.  That  the  spec- 
trum of  a  compound  which  is  dissociated  at  1000°  should  be 
visible  in  the  solar  spectrum  appears  somewhat  paradoxical, 
but  Kayser  and  Runge  have  pointed  out  that  the  carbon 
molecule,  as  is  shown  by  its  varying  specific  heat,  is  not  a 
constant  quantity,  and  the  "cyanogen  bands"  maybe  the 
spectrum  of  an  unknown  compound  of  carbon  and  nitrogen 
which  is  capable  of  existence  at  very  high  temperatures. 
The  cyanogen  bands  have  been  measured  by  Liveing  and 
Dewar,  and  the  third,  fourth,  and  fifth  ones  also  by  Kayser 
and  Runge. 

The  carbon  bands  all  have  their  brighter  edges  directed 
towards  the  red  end  of  the  spectrum;  each  possesses  a  number 
of  edges,  varying  from  three  to  seven,  which  become  weaker 
towards  the  violet.  The  lines  extend  from  the  first  edge  of 
one  band  to  the  beginning  of  the  next,  so  that  no  portion  of 
the  spectrum  from  620^  to  34OyUyu  is  free  from  carbon  lines, 
the  total  number  of  which  is  at  least  10,000.  Metallic  spectra 
obtained  by  means  of  the  arc  and  carbon  poles  always  exhibit 

158,  558.  Lielegg,  Wien.  Ber.  (1868)  52.  593.  Troost  and  Hautefeuille,  C. 
r.  (1871)  73,  620.  Wiillner,  P.  A.  (1872)  144,  481.  Salct,  A.  c.  p.  (1873)  [4] 
28,  60.  Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris,  1874).  Wesen- 
donck,  Inaug-Diss.  (Berlin,  1881).  Hartley,  B.  A.  R.  1883.  Eder,  Denkschr. 
Wiener  Akad.  (1890)  57. 


SPECTRA    OF   THE   ELEMENTS.  11$ 

the  metallic  lines  superposed  by  the  carbon  bands,  hence  a 
good  knowledge  of  the  latter  is  very  desirable. 
Line-spectrum: 


6584.0         6578.5         5695.1         5661.9         5647.5 
4266.6         3920.0         2837.2         2836.3         2746.5 
2509.0         2478.3         2296.5 

Band-spectrum: 

I.  Orange  Band  6187  —  5954:        6188.2      6119.9      6057.3 

5145.0 
2511.9 

6001.8 

5954-5 

II.   Green-yellow  Band: 

i.   Edge:    5635.3 

5634-3 

5633.9 

5633.4 

5632.9 

5632.2 

5631-6 

5630.9 

5630.1 

5629.3 

5628.5 

5627.6 

5626.7 

5625.8 

5624.4 

5623.1 

5620.4 

5619.6 

5618.8 

5617.8 

5615.6 

5613-8 

5611.8 

5610.1 

5608.5 

5606.1 

5603.5 

5600.8 

5598.0 

5595-3 

5592-5 

5589-7 

5588.1 

5587.4 

5585.5 

2.   Edge:    5584.4 

5582.1 

5578.8 

5578.5 

5578.2 

5577-1 

5575-5 

5573-2 

5572-8 

5572-4 

557L  I 

5570.1 

5569.5 

5568.3 

5567.2 

5566.7 

5565.0 

5564-3 

5563.9 

5563.5 

5561.4 

5560.5 

556o.o 

5558.1 

5556.3 

5556.0 

5555-7 

5554-1 

5552-9 

5552.6 

5540.9 

(3-  Edge) 

;    . 

III.  Green  Band: 

I.   Edge:    5165.4 

5165.2 

5164.9 

5164.6 

5164-5 

5163-7 

51^3.2 

5162.7 

5162.5 

5162.0 

5161.3 

5160.5 

5160.0 

5158.7 

5157.8 

5157.3 

5156.2 

5155.3 

5I54.5 

5154-4 

5I53.4 

5153.0 

5152-6 

5152.0 

5150.8 

5149.2 

5147-8 

5146.2 

5144.7 

5143.0 

5I4I-3 

5139-4 

5137.7 

5135.7 

5133.8 

5I3L7 

5129-7 

5129.4 

2.   Edge:    5129.4 

5129-3 

5129.0 

5128.8 

5127.8 

5127-4 

5126.2 

5125.4 

5124-9 

5123-9 

5122.9 

5121.8 

5121.6 

5II9.3- 

5118.2 

5116.8 

5H5.9 

5H4.4 

5113.2 

5111.8 

5110.8 

5110.2 

5109.2 

5108.0 

5106.5 

5105.5 

5103.9 

5103.5 

5102.6 

5101.0 

5099.9 

5098.2 

5096.9 

5095.3 

5094.2 

5092.4 

5091.6 

5091-0 

5089.3 

5087.6 

5087.1 

5086.4 

5084.9 

5083.1 

5081.9 

5080.  i 

5078.5 

5076.8 

5071.9 

5070.  i 

5068.8 

5066.9 

5066.  i 

5065.1 

5063.7 

5058.1 

5056.3 

5054.8 

5052.8 

5049.7 

5045.4 

5041-5 

5039.9 

5037.9 

(5033.9 

5033-7) 

5032.2 

5030.1 

5026.0 

5024.1 

5022.1 

5017.9 

50I3-9 

5009.6 

5005.6 

5001.1 

4997.0 

4992.5 

4988.3 

4983.7 

4979-4 

4974.6 

4970.3 

4965.4 

4961.0 

4956,1 

4951.6 

4946.  5 

4886.2 

4854.2 

4849.0 

4838.0 

4809.7 

4804.4 

4798.4 

IV.   Blue  Band: 

i.   Edge:    4737-2 

4736.4 

4735-9 

4735-5 

4735-1 

4734-6 

4734-1 

4733-6 

4733-0 

4732-4 

4732-0 

4731-0 

4730.0 

4729.4 

SPECTRUM  ANALYSIS. 


4728.4 

4727-1 

4726.2 

4725.1 

4724.0 

4723.6 

4722.3 

4721.2 

4719-9 

4718.8 

4717-4 

4716.8 

4715.4 

2.  Edge: 

4715.2 

4714-1 

47I3.3 

47II-7 

47io.5 

4708.6 

4707.2 

4706.9 

4705.9 

4704.0 

4702.6 

4702.1 

4699-9 

4699.4 

4698.4 

4697.6 

3-  Edge: 

4697.2 

4695-6 

4695.3 

4694.2 

4693.9 

4692.8 

4691.2 

4690.7 

4689.5 

4688.3 

4687.4 

4686.2 

4685.0 

4.  Edge: 

4684.7 

4683.2 

4682.5 

4682.0 

4681.0 

4679-8 

4679.5 

4677.6 

4675.8 

4675.0 

4674.1 

4673-8 

4673-1 

4672.8 

4671.8 

4671.4 

4671.0 

4670.4 

4669.8 

4669.2 

4668.6 

4667.7 

4666.9 

4666.5 

4665.6 

4664.4 

4664.  i 

4663.0 

4661.3 

4659-9 

4658.9 

4657.9 

4657.1 

4656.8 

4654-6 

4653-7 

4652.3 

4652.0 

V.  Band:     i.   Edge  4382.0     2.   Edge  4371.4     3.  Edge  4365.1 


5182.5          5I79.5 
4823.55       4821. 3  b 
4394. 7  br  (A.  andTh.) 


CARBON   MONOXIDE.1 

6079  5609  5198  br  5187.5  5184.5 

5176.0  5173.5  5170  5167.2  4834.5  b' 

4819.  i  b  4817.0  b  (4789.8  b  4786. 5  b)  4509.8  b* 

3493-3  br  3307. 5  b>-  3134.6^  2976.3  b^  3832.0 br  2792.7  br  2665.1^ 

2599. ob*  2510.8^  2435. ob*  2425. ob*  2404.7^  2394.0  bv  2381. 5  b» 

2364.8  b*  2337. 7  bv  2311. 4b*  2286. 2  bv  2220 bv   2215. 3  bv  2188. i  b" 

2172.3  b*  2161. 6  b*  2149.9  b*  2127. 8  br  2112. 7  bv  2089. 3  br  2066.8  b' 

<(Deslandres). 

The  bands  marked  br  are  sharply  defined  towards  the  red 
and  shade  off  towards  the  violet ;  those  marked  b"  are  sharply 
defined  towards  the  violet  and  shade  off  towards  the  red. 


I.   Band: 
4601        4575 

CYANOGEN." 

4551         4533         45i6         4506         4501 

II.   Band: 

i.   Edge:   4216.17 

4215-67 

4215-31 

4215-04 

4214.76 

4214.08 

4213.71 

4213.29 

4212.85 

4212.39 

4211.90 

4211.37 

4211.03 

4210.82 

4210.23 

4209.62 

4208.98 

4208.29 

1  Angstrom  and  Thalen,  N.  A.   S.    U.   (1875)  9.     Deslandres,  A.  c.  p. 
<i888)  [6]  14,  5,  257.    Pliicker,  P.  A.  (1858)  105,  77;  (1859)  107,  533.  Watts, 
P.  M.  (1869)  [4]  38,  249;  41,  12.     Wullner,  P.  A.  (1872)  144,  481.       Wesen- 
donck,  W.   A.  (N.  F.)  (1881)  17,  427.     AngstrOm,  P.  A.  94,  141.     Thollon, 
A.  c.  p.  (1881)  [5]  25,  287.      Piazzi-Smyth,  P.  T.  E.  30,  94.     P.  M.   [4]  49, 
24.     A.  S.  Herschell,  P.  T.  E.  30,  152. 

2  Kayser  and  Runge,  A.  B.  A.  1889.     Liveing  and  Dewar,  P.    R.  S.  30, 
494;  33,  403;  34,  123.    Fox-Talbot,  P.  M.  [3]  4,  114.    Dibbits,  De  Spectraal 


SPECTRA    OF   THE   ELEMENTS. 


4207.59 

4206.85 

4206.08 

4205.30 

4204.46 

4203.61 

4202.70 

4202.17 

4200.85 

4198.85 

4197.82 

4197.29 

2.  Edge: 

4197.29 

4196.10 

4193.08 

4191.51 

4190.30 

4189.68 

4189.07 

4185.89 

4185-09 

4182.44 

4181.52 

4181.03 

3.  Edge: 

4178.01 

-41/7-53 

4175.04 

4171.87 

4167.82 

4.  Edge: 

4I65-54 

4165-24 

4163.54 

4161.80 

4161.43 

4160.01 

5-  Edge: 

4158.22 

6.  Edge: 

4152.93 

4149.31 

4146.06 

4143.12 

4140.94 

4140.34 

4I37-44 

4i33-8i 

4133.44 

4131-24 

4128.19 

4126.72 

4124.30 

4122.35 

4119.48 

4114.20 

4110.04 

4106.78 

4102.89 

4099.27 

4097.04 

4092.98 

4090.95 

4090.25 

4087.93 

4083.31 

4077.89 

4076.06 

4073.74 

4069.38 

4053.40 

4051-05 

4034-61 

III.  Band: 

i.  Edge: 

3883.60 

3880.63 

3880.26 

3879.90 

3879.50 

3879.08 

3878.65 

3876.12 

3874.37 

3873.17 

3872.93 

3872.42 

2.  Edge: 

3871.59 

3870.32 

3870.12 

3866.18 

3864.49 

3863-57 

3862.69 

3862  03 

3-  Edge: 

3861.91 

3860.83 

3859-85 

3858.86 

3857.87 

3856.87 

3855.81 

4.  Edge: 

3855-06 

3852.59 

3851-46 

3850.35 

3849.19 

3848.03 

3845-63 

3845-06 

3844.40 

3843.17 

3841.91 

3840.63 

3834--00 

3839.34 

3838-02 

3836.69 

3835.34 

3833.98 

3832.60 

3832.01 

5831.20 

3830.80 

3829.79 

3828.36 

3826.89 

3825.45 

3823-95 

3822.48 

3821.93 

3820.94 

3819-41 

3817-84 

3816.29 

3814.72 

3811.49 

3809.87 

3808.53 

3806.56 

3804.86 

3803.21 

3801.48 

3800.19 

3799.78 

3798.05 

3797-07 

3796.28 

3793.89 

3792.75 

3792.27 

3787.32 

3783.65 

3781.80 

3779.92 

3778.03 

3777-23 

3776.12 

3775-40 

3774-21 

3773.65 

3772.29 

3771.92 

3768.42 

3764-46 

3762.46 

376i.i3 

3760.47 

3758.45 

3756.45 

3752.38 

3746.19 

3744-11 

3742.00 

3739-90 

3738.55 

3736.62 

3733-54 

373L4I 

3729.25 

3728.86 

3727-II 

3724.95 

3722.78 

3720.60 

3720.12 

3718.42 

3716.23 

3714.03 

3713.06 

37H.85 

3709-65 

3705.*5 

3702.96 

3700.75 

3698.52 

3697.16 

3696.28 

3694-05 

3691.79 

3689.55 

3685.05 

3682.82 

3681.37 

Analyse.  1863.  P.  A.  (1864)  122,  497.  Draper,  P.  M.  (1848)  [3]  32,  108. 
Morren,  A.  c.  p.  (1865)  [4]  4,  305.  Plucker  and  Hittorf,  P.  T.  155,  i. 
Jahresber.  1864,  p.  no.  A.  Mitscherlich,  P.  A.  121,  459.  Watts,  P.  M. 
<i868)  [4]  38,  249;  (1871)  41,  12.  Wiillner,  P.  A.  (1871)  144,  517.  Lockyer, 
P.  R.  S.  27,  308.  Ciamician,  Wien.  Ber.  1880.  Wesendonck,  W.  A.  (N.  F.) 
<i88i)  17,  427.  A.  S.  Herschell,  P.  T.  E.  30,  154.  Thalen,  Le  spectre  du 
ier.  1884.  Deslandres,  A.  c.  p.  (1888)  [6]  14,  5. 


u6 


SPECTRUM  ANALYSIS. 


3680.55 

3679.40 

3678.30 

3676.05 

3673.79 

367L54 

3669.78 

3669.30 

3667.04 

3664.81 

3662.57 

3662.26 

3658.09 

3655-86 

3653.66 

3651.45 

3648.03 

3644.30 

3642.67 

3641.15 

3640.  50 

3638.33 

3637-31 

3636.39 

3635-24 

3633.09 

3631.65 

3629.35 

3624.22 

3619-17 

3607.92 

3607.44 

3606.98 

3606.51 

3606.05 

3605.60 

3605.13 

3604.73 

3604.27 

3602.95 

3597.89 

3594-30 

3593-86 

3593.44 

IV.  Band: 

i.  Edge:  3590.52 

2.  Edge:  3585.99' 

3,  Edge:  3584,10 

3583.38 

3582.01 

3581.76 

3580.39 

3580.07 

3579-26 

3578.93 

3578.62 

3578.28 

.  3577.23 

3576.88 

3576.48 

3575-73 

3575-13 

3574-50 

3573.87 

3572.6o 

3571-93 

357L27 

3570.59 

3569-96 

3569-89 

3569.17 

3568.44 

3567.53 

3567.02 

3566.93 

3566.27 

3564.95 

3563.96 

3561.60 

3561.42 

3560.75 

3557.34 

3556.13 

3554-48 

3553.72 

3552.86 

3549-  ii 

3548.67 

3548.36 

3545-92 

3545-11 

3540-53 

3540.10 

3537-66 

3534-75 

3530.35 

3528.75 

3527.74 

3524-70 

3524.51 

3523.51 

3520.01 

35I7.I6 

3512.79 

35H.65 

3510.38 

3509-4& 

3506.65 

3503.83 

3501.67 

3497.21 

CERIUM. 

The  spark-spectrum  of  cerium  is  obtained  by  the  use  of 
the  chloride.  In  the  arc-spectrum  Lockyer  l  has  observed  32 
additional  lines  between  A  =  3900  and  4012. 

Spark-spectrum: 

5512.2  5409.7  5393.7  5353.1  5274.2  4714.5  4629.0  4573.4 
4562.9  4561.4  4540.4  4528.4  4527.4  4523.9  4460.3  4428.8 
4392.2  4386.2  4382.7  4296.6  4289.6 


CHLORINE. 

The  line-spectrum  is  obtained  by  the  passage  of  an  elec- 
tric discharge  through  a  vacuum-tube,  or  through  chlorine 
under  the  ordinary  pressure,  and  also  by  short  sparks  between 
platinum  electrodes  immersed  in  hydrochloric  acid.  Hassel- 

1  P.  R.  S.  27,  280.     P.  T.  1881,  3.     See  also  Thalen,  N.  A.  S.  U.   [3]  6. 
Kirchhoff,  A.  B.  A.  1861.     Bunsen,  P.  A.  155,  366. 


SPECTRA    OF   THE   ELEMENTS.  I  I'/ 

berg l  observed  that  the  chlorine-spectrum  is  produced  by 
passing  powerful  sparks  through  glass  tubes  containing 
chlorine  compounds  under  low  pressure.  The  spectrum 
obtained  with  a  powerful  continuous  current  differs  from  that 
produced  when  a  condenser  is  introduced  into  the  circuit.2 

There  are  no  recent  measurements  of  the  absorption- 
spectrum  of  chlorine. 

Spark-spectrum : 

5457.8     5444.7     5425-0     5393-4    (5220.8     52172)    5103.2     5099.0 
5078.4     4918.1    (4905-4     4897.8)    4820.8     4810.7     4794-9 

Absorption-spectrum:8  Numerous  absorption-bands  in  the 
green  and  blue,  total  extinction  in  the  violet. 

CHROMIUM. 

The  arc-spectrum  of  chromium  between  D  and  A  =  3430 
has  been  accurately  measured  by  Hasselberg.4  Huggins5and 
Thalen  6  had  previously  investigated  lines  of  the  spark-spec- 
trum in  the  visible  region,  Lockyer7  observed  some  additional 
lines  between  A  =  4000  and  3900,  and  Liveing  and  Dewar8 
worked  on  the  ultra-violet  portion  of  the  arc-spectrum.  Solu- 
tions of  chromium  compounds  produce  characteristic  absorp- 

1  Bull.  Acad.  St.  Petersb.  28,  405.     See  also  Van  der   Willigen,    P.   A. 
106,  624.     Ditte,  C.   r.   73,  622.     Plucker,    P.   A.    107,   528.     Pliicker  and 
Hittorf,  P.  T.  155,  i.     Angstrom.  C.  r.  73,  369.     Thalen,  K.  Svenska  Ve- 
tensk.  Akad.  Handl.  12,  No.  4,  p.  8.     Salet,  A.  c.  p.  [4]  28,  24.    Ciamician, 
Wien.  Ber.  78,  872. 

2  Trowbridge  and  Richards,  Amer.  Jour.  Sci.   (1897)  [4]   3,  117.     P.  M. 
43,   135. 

3  Morren,  P.  A.  (1869)  137,  165.     Sillim.  Journ.  [2]  47,  417. 
Svensk.  Vetensk.  Akad.  Handl.  (1894)  28,  N.  5. 

P.  T.  (1864)  154,  139. 

N.  A.  S.  U.  [3]  6. 

P.  T.  1881. 

P.  R.  S.  (1881)  32,  402.  See  also  H.  W.  Vogel,  Monatsber.  Berl.  Akad. 
1878,  p.  413.  Ber.  8,  1533.  Kirchhoff,  A.  B.  A.  1861.  Angstrom,  Recher- 
ches  sur  le  spectre  solaire.  1868.  Lecoq  de  Boisbaudran,  Spectres  lumi- 
neux  (Paris,  1874). 


Il8  SPECTRUM  ANALYSIS. 

tion-spectra '  that  have  been  frequently  studied;  the  more 
important  are  shown  in  Fig.  41,  Chapter  VIII.  The  spectro- 
scopic  determination  of  potassium  chromate,  potassium 
bichromate,  and  chrome  alum  is  described  in  G.  and  H.  Kruss* 
work  on  Colorimetry  and  Quantitative  Spectrum  Analysis. 
Arc-spectrum: 


5791-20 

5788.15 

5785.21 

5784.09 

5698.55 

5409.99 

5400.82 

5348.50 

5345-98 

5329-30 

5328.50 

5300.90 

5298.43 

5298.14 

5297-52 

5296.86 

5276.20 

5275.85 

5275.31 

5265.88 

5264.32 

5255.27 

5247.68 

5225.08 

5208.58 

5206.20 

5204.67 

5196.60 

4954.92 

4942.63 

4936.51 

4922.40 

4887.15 

4870.96 

4862.00 

4829.50 

4801.17 

4792.61 

4789.45 

4756.30 

4737.50 

4730.88 

4718.57 

4708.16 

4698.77 

4698.60 

4689.54 

4666.67 

4664.94 

4663.98 

4663.47 

4652.31 

4651.44 

4646.33 

4926.31 

4622.60 

4622.07 

4616.28 

4613.54 

4600.92 

4595.78 

459I-56 

4580.22 

4571.85 

4569.76 

4565.71 

4546.15 

4544-77 

4540.90 

4540-70 

4539-96 

4535.95 

4530.92 

4527.53 

4526.65 

4512.05 

4497.02 

4385.11 

4374-34 

4373-41 

4371-44 

4359-78 

435L9I 

4351.20 

4344.66 

4339-85 

4339-60 

4289.87 

4274.91 

4263.28 

4254.49 

4163.76 

4153.96 

4126.67 

4067.05 

3991.26 

3984.02 

3976.81 

3971-39 

3969.89 

3963-82 

3928.79 

3921.20 

39T9.3I 

3916.38 

3915.96 

3908.87 

3903.02 

3894.20 

3886.94 

3885.35 

3883.41 

3857.74 

3854.36 

3850.13 

3841-42 

3830.17 

3804.91 

3797.85 

3749-13 

3744-01 

3743-67 

3656.36 

3649-12 

3641.95 

3639-93 

3605.46 

3593.57 

3578.81 

3550.73 

3465.40 

COBALT. 

The  line-spectrum  of  cobalt,  in  the  visible  field,  has  been 
frequently  investigated  by  the  earlier  workers.  Kirchhoff,2 
Huggins,3  Thalen,4  Lecoq  de  Boisbaudran,5  and  Schuster 
examined  the  spark-spectrum,  and  Angstrom6  and  Thalen 

1  Brewster,  P.  A.  (1836)  37,  315.  Erhard,  Inaug.-Diss.  (Leipzig,  1875). 
Miiller,  P.  A.  (1847)  72,  67.  H.  W.  Vogel,  Ber.  (1875)  8,  1533.  Monatsber. 
Berl.  Akad.  1878,  p.  413.  Stoney  and  Reynolds,  B.  A.  R.  1878.  Sabatier, 
C.  R.  (1886)  103,  49.  Lapraik,  J.  pr.  Chem.  1893  [2]  47,  305.  Etard,  C.  r. 
(1895)  120,  1057- 

8  A.  B.  A.  1861. 

3  P.  T.  1864,  139. 

4  N.  A.  S.  U.  [3]  6.     From  A  3998.0  -  A  2244.8. 

5  Spectres  lumineux  (Paris,  1874). 

*  Recherches  sur  le  spectre  solaire,  1868. 


SPECTRA    OF   THE   ELEMENTS.  119 

that  of  the  arc;  Lockyer  '  and  Cornu  2  have  also  investigated 
portions  of  the  spectrum.  Hasselberg 8  has  recently  measured 
the  lines  of  the  arc-spectrum  between  D  and  A.  =  3450,  and 
Liveing  and  Devvar,4  those  of  the  arc  and  spark  spectra  in  the 
ultra-violet  region.  The  lines  of  the  two  spectra  differ  not 
only  in  number,  but  also  in  intensity.  The  absorption-spectra 
of  cobalt  glass,  and  of  solutions  of  cobalt  compounds  are  very 
characteristic;  they  have  been  examined  by  H.  W.  Vogel,5 
Russell,6  Russell  and  Orsman,7  and  by  C.  H.  Wolff,8  and  are 
shown  in  Fig.  41,  Chapter  VIII.  The  following  test  is  stated 
by  Wolff  to  be  one  of  the  most  delicate  known  in  chemistry: 
Ammonium  thiocyanate  is  mixed  with  cobalt  chloride  solu- 
tion, and  shaken  with  amyl  alcohol  and  ether;  this  dissolves- 
the  cobalt  thiocyanate,  and  the  solution  gives  a  characteristic 
absorption-spectrum.  The  method  was  used  for  the  spectro- 
colorimetric  determination  of  cobalt  when  present  in  small 
quantity.  The  absorption-spectrum  of  cobalt  chloride  in 
hydrochloric  acid  solution  is  stated  by  W.  J.  Russell  to  be 
particularly  sharp,  but  if  the  acid  is  concentrated  the  broad 
bands  usually  observed  are  resolved  into  smaller  ones,  almost 
coincident  with  those  produced  by  ferric  chloride  under  the 
same  conditions.  He  believes  that  the  solvent  causes  a  dis- 
sociation of  the  dissolved  substance. 
Arc  and  spark  spectra: 

6143.8*   6122.3*   553i-o(>   5525.27   5523-56   5489.90   5484.22 
5483.57   5477-13   5454-79   5444-Si   5407.75   5381.99   5369.79 

1  P.  T.  1881.  Part  3. 

2  Spectre  normal  du  soleil  (Paris,  1881). 

3  Svenska,  Vetensk.  Akad.  Forhandl.  (1896)  28,  No.  6.   From  D  —  A. 3450. 
Astrophys.  Jour.  (1896)  3,  288;  4,  343;  (1897)  5,  38. 

4  P.  T.  (1888)  179,  231.     From  A.  3450-2244. 

5  Ber.  11,  916.     Monatsber.  Berl.  Akad.  1878,  p.  415. 

6  P.  R.  S.  31,  51.     Ber.  14,  503. 

7  J.   Chem.  Soc.  1889,  p.  14.      Ber.  24,  619. 

8  Zeitschr.  Anal.  Chem.  18,  38.     See  also  Etard,  C.  r.  (1895)  120,  1057. 


*  Visible  only  in  the  spark-spectrum, 


120 


SPECTRUM  ANALYSIS. 


5362.97 

5359.41 

5353.69 

5352.22 

5343.58 

5342.86 

534L53 

5331.65 

5325.44 

5316.96 

5312.84' 

5301.24 

5280.85 

5276.38 

5268.72 

5266.71 

5266.51 

5257.81 

5248.12 

5235.37 

5230.38 

5212.87 

5176.27 

5156.53 

5154.26 

5146.96 

5133.65 

5126.37 

5125.88 

5123-01 

5H3.4I 

5109.08 

5095.18 

4988.15 

4980.15 

4972.16 

4966.77 

4928.48 

4904.37 

4899-72 

4882.90 

4868.05 

4843.61 

4840.42 

(4814.16 

4813.67) 

4796.00 

4793.03 

4785.26  ' 

4781.62 

4780.14 

4778.42 

4776.49 

4771.27 

4768.26 

4767.33 

4754-59 

4749.80 

4737-95 

4735.04 

4728.14 

4718.67 

4698.60 

4693.37 

4682.53 

4663.58 

4657.56 

4644.48 

4629.47 

4625.88 

4623.15 

4597-02 

4594-75 

4581.76 

4580.32 

457o.i8 

4566.77 

4565.74 

4549.80 

4546.14 

4543.99 

4534.18 

4531.14 

4517.28 

45I4.33 

4494.92 

4484.07 

4483.70 

4478.45 

4471.70 

4469.72 

4467.04 

4445.88 

4421.48 

4417.55 

4392-02 

4391.70 

4380.25 

4375-09 

4373-77 

4371.27 

4339.76 

4331.38 

4303.36 

4285.93 

4252.47 

4234.18 

4190.87 

4162.33 

4158.58 

4121.47 

4118.92 

4110.69 

4086.47 

4082.76 

4077.55 

4076.28 

4068.72 

4066.52 

4058.75 

4058.36 

4053.08 

4045.53 

4035.73 

4027.21 

4021.05 

3998.04 

3995.45 

3979-65 

3978.8o 

3974-87 

3973.29 

3969-25 

3958.06 

3953.05 

3945-47 

3941.87 

3941.01 

3936  12 

3922.88 

3917.26 

3910.08 

3906.42 

3895.12 

3894.21 

3884-76 

3882.04 

3876.99 

3874-10 

3873.25 

3861.29 

3851.09 

3845.95 

3842.20 

3816.58 

3816.46 

3755-59 

3750.06 

3745-61 

3736.05 

3734.30 

3733-62 

3732.52 

3730.61 

3708.96 

3702.40 

3693.65 

3693.27 

3684.62 

3683.18 

3676.69 

3652.68 

3649.47 

3647.82 

3643.34 

3641-95 

3639-63 

3634.86 

3633.00 

3631-55 

3627.96 

3625.13 

3611.89 

3605.50 

3595-00 

3587.30 

3585-28 

3584.92 

3575.48 

3575.06 

3569.48 

3565-08 

3563-04 

3562.22 

3561.01 

3558.90 

(3553-12 

3552.85) 

3550.72 

3548.6o 

3543.40 

3533-49 

3529.92 

3529-17 

3526.96 

3523.85 

3523-57 

3521.70 

3520.20 

3518.49 

3513-62 

3512.78 

3510.53 

3509-98 

3506.44 

3502.76 

3502.41 

3496.83 

3495.82 

3491.46 

3490.89 

3489.54 

3485.49 

3483.55 

3474-15 

347L52 

3466.0 

3462.9 

3453-6 

3449-3 

3443-7 

(3434.0 

3433.5) 

3432.0 

(34I3-7 

34I3.4 

3410-3 

3406.0 

3396.5 

3389-3 

3388.8 

3381.7 

3368.3 

3356.4 

3336.1) 

3284.9 

3158.6 

3154-6 

3147.0 

3I39.9 

3137.4 

3121.5 

3086.7 

3082.5 

3072.4 

3061.9 

3049-0 

3044.0 

2989-5 

2986.9 

2954.5* 

2942.9 

2824.9 

2648.8 

2580.2 

2564.0 

2541.9 

2540.6 

2533-8* 

2532.1 

2530.0 

2528.5 

2524.9* 

2524.6 

2521.1 

2519.7* 

2510.9 

2506.2 

2497-5 

2490.  2 

2464.  i 

2436.9 

2432.4 

2420.7 

2417.6 

2411.6 

2407.5 

2397-3 

2388.8 

2378.5 

2363-7 

2353-4 

23I3-9 

23H.5 

2307.8 

2293.4 

2286.1 

2266.6* 

2260.1* 

2256.8* 

2245.2* 

*  Visible  only  in  the  spark-spectrum^ 


SPECTRA    OF   THE  ELEMENTS.  121 


COPPER. 

The  spark-spectrum  of  copper,  in  the  visible  field,  has  been 
measured  by  Kirchhoff,1  and  Thal6n,2  and,  as  far  as  wave- 
length 4275,  by  Lecoq  de  Boisbaudran ;3  in  the  ultra-violet 
Hartley  and  Adeney 4  have  measured  the  portion  between 
A  =  3999  and  2103,  and  Trowbridge  and  Sabine 5  that 
between  A  =  2369  and  1944.  Liveing  and  Dewar6  have 
photographed  the  arc-spectrum  from  A  =  2294-2135,  whilst, 
more  recently,  Kayser  and  Runge  7  have  done  the  same  for  the 
region  between  X.  =  6000  and  1944;  they  measured  304  lines, 
and  obtained  the  spectrum  by  substituting,  for  the  carbon 
poles,  rods  of  copper  1-2  sq.  cm.  in  section. 

Scarcely  any  of  the  copper  lines  are  sharply  defined  even 
on  one  side,  so  that  the  spectrum  has  a  peculiar  appearance. 
In  the  Bunsen  flame  cupric  chloride  produces  a  band-spectrum 
extending  over  the  whole  field,  with  the  exception  of  the 
violet;  the  same  spectrum  is  obtained  with  the  metal  if  the 
flame  contains  hydrogen  chloride.  The  absorption-spectra  of 
copper  salts  are  not  characteristic,  as  the  compounds  produce 
total  extinction  both  in  the  red  and  the  violet.  Ewan  8  found 
that,  in  aqueous  solution,  the  spectra  of  the  chloride,  sul- 
phate, and  nitrate  change  with  progressive  dilution  tending  to 
become  identical;  this  observation  is  in  agreement  with  the 
theory  of  electrolytic  dissociation.  C.  H.  Wolff9  has  sug- 
gested a  spectro-colorimetric  method  for  the  determination  of 


A.  B.  A.  1861. 

N.  A.  S.  U.  (1868)  6. 

Spectres  lumineux  (Paris,  1874). 

P.  T.  (1883)  175,  63. 

Proc.  Amer.  Academy,  1888.     P.  M.  [5]  26,  342. 

P.  R.  S.  (1879)  24,  402.     P.  T.  (1883)  174,  205. 

A.  B.  A.  1892. 

8  P.  M.  1892,  p.  317.     Ber.  25,  4950.     P.  R.  S.  (1895)  57,  128. 

9  Zeitschr.  anal.  Chem.  18,  38. 


122  SPECTRUM  ANALYSIS. 

copper  in  small  quantity,  and  P.   Sabatier  *  has  studied  the 
absorption-spectra  of  solutions  of  cupric  bromide. 
Arc  and  spark  spectra: 


5782.30 
4704.77 
4480.59 
3602.11 
3247.65 
2618.46 
2303.18 
2199.77 

5700.39 
4674.98 

4415.79 
3599-20 
3126.22 
2492.22 
2293.92 
2178.97 

5292.75 

4651-31 
4378.40 

3512.19 
3108.64 
2441.72 
2263.20 
2165.20 

5220.25 
4587.19 

3450.47 
3063.50 
2406.82 
2230.16 
2104.88 

5218.45 

4539-98 
4259.63 
3308.10 
3036.17 
2392.71 
2227.85 
2025.14 

5153-33 
453I-04 
4062.94 

3290.62 
2961.25 
2370.5* 
2225.77 
1943-88 

5105.75 
4507.62 
4022.83 
3274.06 

2766.50 
2369.97 
2214.68 

CUPRIC   CHLORIDE.2 
Flame-spectrum: 

6619  b  6268  bv  6151  b7'  6051  bv  5564  b  5507  5440  5386 

5306  b  5270  b  5240  5088  b7'  5050  bv  4984  bv  4946  bv  4883  bv 

4848  b"  4793  b"  458o  fa"  4523  b»  4497  bv  4437  b"  4413  b"  4354  bw 

4332  b"  4282  bv  4261  bv 

DIDYMIUM.3 

The  metals  of  the  rare  earths  have  been  frequently  inves- 
tigated during  the  past  few  years,  and  new  substances  have 
been  discovered  in  bodies  which  were  formerly  believed  to  be 
elementary.  In  1885  didymium  was  resolved  into  neodymium 
and  praseodymium,  and  samarium,  which  was  discovered  in 
1879,  was  also  shown  to  be  present.  Other  members  of  the 
cerium  and  yttrium  groups  have  likewise  been  decomposed 
into  its  elements.  At  present  the  chemical  properties  of  these 


1  C.  r.  118,  1042,  1144.      Ber.  27,  489,  490.      See  also  Glan.  W.  A.  (1878) 
3,  65.      Kriiss.  Colorimetrie  (Hamburg,  1891). 

2  Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris,  1874).   Diacon,  A.  c. 
p.  (1865)  [4]  6,  5.     A.  Mitscherlich,  P.  A.  116,  499;  (1863)  121,  459. 

3  Thalen,    Om  Spectra  tillhoranda  Yttrium,  Erbium,   Didym  och  Lan- 
than  (Stockholm,  1878).  Ofersigt  K.  Vetenskaps  Akad.  Forhandl.  (1883)  40, 
No.  7.    Gladstone,  J.  Chem.  Soc.  10,  219.    Bunsen,  P.  A.  155,  366.    Kirch- 
hoff,  A.  B.  A.  1861.     Delafontaine,  P.  A.  124,  635.     Lockyer,  P.  T.  1881. 


*  Visible  only  in  the  spark-spectrum.     (Hartley  and  Adeney.) 


SPECTRA    OF   THE  ELEMENTS.  12$ 

substances  have  not  been  sufficiently  studied  to  render  their 
recognition  as  elements  absolutely  free  from  doubt.  Kriiss 
and  Nilson,  as  the  result  of  their  investigation  of  the  absorp- 
tion-spectra, consider  that  didymium,  erbium,  holmium, 
samarium,  and  thulium  are  composed  of  more  than  twenty 
elements;  their  conclusion  is  based  on  the  assumption  that 
each  element  has  a  characteristic  maximum  of  absorption,  but 
Schottlander's  extensive  investigations  show  that  this  is  falla- 
cious. Bailey  has  also  raised  objections  to  Kruss  and  Nil- 
son's  conclusions.  At  present  the  results  of  the  spectroscopic 
work  on  the  rare  earths  is  so  uncertain,  that  the  data  given  in 
this  book  usually  refer  to  the  "  old  "  elements.  Bahr  and 
Bunsen  found  that  didymium  oxide,  like  erbium  oxide,  when 
heated  in  the  Bunsen  flame  gives  a  continuous  spectrum,  and 
also  characteristic  bright  lines  which  are  almost  coincident 
with  the  absorption-lines  exhibited  by  solutions  of  the  salts, 
or  by  glass  which  contains  the  metal;  this  is  no  exception  to 
the  rule  that  solids  only  yield  continuous  spectra,  for  Huggins 
and  Reynolds  showed  that  the  earths  are  volatile  in  the  oxy- 
hydrogen  flame.  Comparison  of  the  absorption-spectra  of 
didymium  chloride,  sulphate,  and  acetate  led  Bunsen  to  the 
conclusion  that  the  bands  tend  to  approach  the  red  as  the 
molecular  weight  increases.  The  absorption-spectra  of  the 
rare  earths  in  the  ultraviolet  has  been  investigated  by  Soret. 
Spark-spectrum: 


5486.0* 

5372.0 

5361.5 

5319.9 

5293.5 

5273.5 

5249.5 

5192.5 

5191-5 

5130.3 

4924.5 

4463-2 

4452.3 

4446.7 

4328.1 

4303.6 

4109.8 

4060.  7 

*  Due  possibly  to  samarium. 


124  SPECTRUM  ANALYSIS. 

DIDYMIUM    CHLORIDE. 

Absorption-spectrum  :l 

b  (7431-7*        736i.7*  7308.7*)  6895.6*  6793-3*  l>]b(5963t 

5886f  5824*  5789*  5748*  5720)  [/3]  b  (5313* 

5206)  (5125.8*  5088*)  4823!  4759  4692f 

4441.7 

"OLD"  DIDYMIUM    NITRATE. 
Absorption-spectrum:  positions  of  minimum  of  brightness: 

7291  6906  6794  6407  6235  6189  5797  5759  5317 
5253  5217  5147  5126  4826  4771  4695  4633  4443 
4341  4289.6  4173.6 

PRASEODYMIUM    NITRATE. 
7291       6794      5916      5797      5759      5317      5217      5125      4826      4695      4443 

ERBIUM.2 

The  remarks  on  didymium  apply  also  to  this  element. 
Spark-spectrum : 

5827  5763  5344-4  5257  52i8  5189  4952 

4899.9         4872.4         4820  4674.9         4606.3         4501.3 

1  Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris,  1874).  C.  r.  (1887) 
105,  276.  Bunsen,  P.  A.  155,  366.  Ann.  Chem.  Pharm.  128,  100;  131, 
255.  Huggins  and  Reynolds,  P.  R.  S.  18,  546.  Lippich,  Sillim.  Journ. 
(1873)  [3]  13,  304.  Auer  v.  Welsbach,  Sitzungsber.  Wien.  Akad.  (1885)  92. 
Crookes,  C.  N.  54,  27.  Schuster  and  Bailey,  B.  A.  R.  1883.  H.  Becquerel, 
C.  r.  104,  777,  1691;  106,  106.  Haitinger,  Monatsch.  f.  Chem.  (1891)  12, 
362.  Soret,  C.  r.  86,  1062;  88,  422;  91,  378.  Kriiss  and  Nilson,  Ber.  20, 
2143.  Bailey,  Ber.  (1887)  20,  2769,  3325.  Schottlander,  Ber.  (1892)  25, 
569- 

*  Thalen,  Om  Spectra  Yttrium,  Erbium,  Didym  och  Lanthan  (Stock- 
holm, 1874).  Ofversigt  K.  Vetensk.  Akad.  Forhandl.  (1881)  40.  Bunsen 
and  Bahr,  Ann.  Chem.  Pharm.  137,  i.  Huggins,  P.  R.  S.  1870.  Bunsen, 
P.  A.  155,  366. 


*  Neodymium. 
f  Praseodymium. 


SPECTRA    OF   THE  ELEMENTS.  12$ 

ERBIUM  CHLORIDE.1 
Absorption-spectrum : 

6839          6671  6535          6405          5410 

5364      [«]  5232  4922  4875  45i6 

FLUORINE. 

There  are  no  accurate  measurements  of  the  spectrum  of 
fluorine.  By  the  passage  of  induction-sparks  through  silicon 
fluoride  Salet 2  obtained  a  beautiful  blue  band-spectrum  of 
the  compound;  the  incission  of  a  Leyden  jar  produced  the 
spark-spectrum  of  fluorine.  Commencing  at  Salet's  last  lines 
Liveing  3  measured  the  flame-spectrum. 
Spark-spectrum: 

6922*    6862*    6782*    6401    6231 

Flame-spectrum : 

6231  6091  6011  5571  5321 

GALLIUM. 

Lecoq  de  Boisbaudran,4  who  discovered  this  element, 
measured  its  spark-spectrum,  and  Liveing  and  Dewar  6  that  of 
the  arc. 

Spark  and  arc  spectra: 

4171          4031 

GERMANIUM. 

The  spark-spectrum  of  germanium  has  been  investigated 
by  Kobb,6  and  by  Lecoq  de  Boisbaudran,7  who  calculated  its 

1  Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris,   1874).     Bunsen,  P. 
A.  155,  366.     Bunsen  and  Bahr,  Ann.  Chem.  Pharm.  137,  i. 

2  A.  c.  p.  (1873)  28,  34. 

3  Proc.  Cambridge  Phil.  Soc.  3,  Pt.  3.    See  also  Mitscherlich,  P.  A.  121, 
476.     Seguin,  C.  r.  (1862)  54,  933. 

4  C.  r.  82,  168. 

6  P.  R.  S.  28,  482. 

6  W.  A.  (1886)  29,  670. 

7  C.  r.  (1886)  102,  1291.     Her.  19,  479. 

*  Only  approximate. 


126  SPECTRUM  ANALYSIS. 

atomic  weight  from  his  measurements.  Rowland  and  Tatnall l 
have  recently  photographed  the  arc-spectrum  between  A,  = 
2300-4600. 

Arc  and  spark  spectra: 

6337    6021    5893    5256.5   5229.5   5210    5178.5   5135 
5131    4814    4743    4685.3  4291-6  4261    4226    4179 

3269.628*  3124.945*  3039.198*  2754.698*  2740.535*  2709.734* 
2691.446*  (2651.709*  2651. 219f)  2592.636*  2417.450* 

GOLD. 

Liveing  and  Dewar 2  measured  three  lines  in  the  ultra-violet 
exhibited  by  the  arc-spectrum,  and  these  were  the  only  ones 
known  when  Kayser  and  Runge  3  commenced  their  investiga- 
tion of  the  region  between  wave-length  6600  and  2280.  They 
usually  employed  fine  gold,  but  occasionally  auric  chloride 
and  carbon  poles.  The  visible  portion  of  the  spark-spectrum 
has  been  measured  by  KirchhofT,4  Huggins,5  Thalen,6  and  G. 
Kruss,7  who  ascribes  the  line  5230.47  to  platinum,  and  not 
to  gold. 

Arc  and  spark  spectra: 

6278.37     5957-24     5837-64     5656.00     5250.47     5064.75     4792.79 
4488.46     4065.22     3122.88     3033.38     3029.32     2932.33     2905.98 

2676.05      2428.06 

HELIUM. 

The  yellow  Z>3-line  of  the  solar  spectrum  was  ascribed, 
until  recently,  to  a  hypothetical  element,  termed  by  Frank- 

1  Astrophys.  Jour.  (1895)  1,  149. 

2  P.  T.  (1882)  174,  2219. 

3  A.  B.  A.  1892. 

4  Ibid.  1 86 1. 

5  P.  T.  1864,  p.  139. 

6  N.  A.  S.  U.  [3]  6. 

7  Lieb.  Ann.  (1887)  238,  30.     See  also  Lecoq  de  Boisbaudran,  Spectres 
lumineux  (Paris,  1874). 

*  Arc-spectrum. 

f  Possibly  a  single  reversed  line. 


SPECTRA    OF   THE   ELEMENTS.  I2/ 

land  helium;  this  was  isolated  by  Ramsay1  in  1895  from 
cleveite,  in  which  it  occurs  together  with  argon;  he  also 
obtained  it  from  certain  meteorites  from  Augusta  Co., 
Virginia.  Cleve2  showed  that  it  is  present,  unaccompanied 
by  argon,  in  cleveite  from  Carlshuus  in  Norway,  and  he 
observed  the  presence  in  its  spectrum  of  five  lines  in  addition 
to  Da.  Deslandres,3  using  a  very  high  dispersion,  measured 
the  following  lines: 

6678  5876.0  5048.4  5016.0  4922.2  4713.35  4471.75 
4437.9  4388.4  4I43-9  4120.9  4026.2  3964.0  3888.75 
3819.7  3705.4  3613-8  3447-7  3187.9  2945.7 

Runge  and  Paschen,4  in  the  course  of  an  investigation  of 
the  gases  from  cleveite,  showed  that  the  line  at  5876.0  is  a 
double  one,  and,  as  the  solar  helium  line  had  always  been 
regarded  as  single,  doubt  was  cast  on  the  identity  of  solar 
and  terrestrial  helium.  This  point  was  speedily  settled  by 
Huggins  and  Hale,5  who  showed  that  the  solar  Z>s-line  is  also 
double.  Kayser6  found  that  a  Geissler  tube  containing  what 
he  supposed  to  be  the  purest  atmospheric  argon  also  showed 
the  Z?3-line,  ^us  affording  proof  that  helium  is  present  in  the 
atmosphere.  Lockyer7  states  that  many  of  the  helium  lines 
coincide  with  some  of  hitherto  unknown  origin  in  the  spectra 
of  the  chromosphere,  and  of  the  white  stars  of  Orion.  Under 
the  influence  of  the  silent  discharge  helium  combines  with 
mercury  and  benzene  or  carbon  bisulphide  to  form  a  com- 
pound resembling  that  of  argon,  but  it  does  not  combine  with 
mercury  alone. 

1  C.  r.  120,  660,  1049.     Ber.  28,  318,  448.     N.  52,  224.    Ramsay,  Collie, 
and  Travers,  Jour.  Chem.  Socy.  (1895)  67,  648. 

2  C.  r.  120,  834.     Ber.  28,  373. 

3  C.  r.  (1895)  120,  mo,  1331. 

4  W.  A.  Beibl.  19,  634. 

5  C.  N.  72,  26. 

6  Ibid.  72,  99. 

1  C.  r.  120,  1103.     P.  R.  S.  58,  67.     See  also  Brauner,  C.   N.   71,   271. 
Palmieri,  Acad.  di  Napoli  Rendic.  (1882)  20,  233. 


128  SPECTRUM  ANALYSIS. 

Berthelot '  and  Runge  and  Paschen  a  have  observed  that 
the  spectrum  of  cleveite  gas  consists  of  six  series,  two  pairs 
of  which  are  characterized  as  subseries,  whilst  two  series  are 
principal  series.  Two  spectra  are  thus  differentiated  which 
are  ascribed  to  two  constituents  of  the  gas,  and  which  bear  a 
striking  similarity  to  the  spectra  of  the  alkalies.  Rydberg3 
has  confirmed  these  conclusions,  and  termed  the  second  con- 
stituent parhelium.  Some  confirmation  was  also  afforded  to 
this  view  by  Ramsay  and  Collie's  researches,  which  resulted 
in  the  separation  of  helium  into  a  lighter  and  a  heavier  por- 
tion; but  Ames  and  Humphreys4  were  unable  to  detect  any 
difference  in  their  spectra,  although  they  used  a  spectroscope 
of  high  dispersive  power.  When  further  separated  the  heavier 
portion  was  found  to  consist  chiefly  of  argon. 

HYDROGEN. 

Two  spectra,  termed  the  elementary  and  compound  line- 
spectra,  are  exhibited  by  hydrogen  in  a  Geissler  tube;  their 
production  depends  on  the  conditions  of  temperature  and 
pressure.  The  former  has  been  measured  by  Angstrom,5 
H.  W.  Vogel,6  Lockyer,7  Huggins,8  Cornu  and  Ames;9  the 
latter  was  first  investigated  by  Pliicker  and  Hittorf,10  but  was 
ascribed  to  acetylene  by  Angstrom,  Berthelot  and  Richard,11 
and  Salet.12  The  incorrectness  of  this  view  was  proved  by 

1  C.  r.  (1897)  124,  113. 

2  Sitzber.  Berl.  Akad.  (1895)  639,  759.     W.  A.  Beibl.  (1895)  19,  884,  885. 
Astrophys.  Jour.  (1896)  3,  4. 

W.  A.  (1896)  58,  674.     Astrophys.  Jour.  (1896)  4,  91. 

Astrophys.  Jour.  (1897)  5,  97. 

P.  A.  (1864)  91,  141;   123,  489;  (1872)  144,  300. 

Berl.  Monatsber.  (1879)  586;  (1880)  190.     Ber.  (1880)  13,  274. 

P.  R.  S.  28,  157  ;  30,  31. 

P.  T.  171,  669. 

P.  M.  (1890^  [5]  30,  33. 

10  P.  T.  (1865)  155,  21.     Pliicker,  P.  A.  107,  407. 

11  C.   R.  68,  810.  1035,  1107,  1546. 

12  A.  c.  p.  [4]  28,  17. 


SPECTRA    OF   THE  ELEMENTS.  129 

Hasselberg's 1  exact  measurements.  In  the  spectrum  of 
C  Puppis  Pickering2  found,  in  addition  to  dark  hydrogen 
lines  and  K,  two  broad  lines  at  A.  =  4633  and  A  =  4688,  and 
a  peculiar  series  of  dark  lines  whose  wave-lengths  are  rhythmi- 
cally related.  These  were  A  —  4544,  4201,  4027,  3925,  3859, 
3816,  3783.  It  was  first  thought  that  they  represented  some 
new  element  not  yet  found  on  the  earth  or  in  the  stars,  but 
they  are  very  probably  due  to  hydrogen,  produced  under 
conditions  of  luminosity  hitherto  unknown.  By  applying 
Balmer's  formula,  Pickering  found  that  the  new  lines  form  a 
harmonic  series.  This  conclusion  was  confirmed  by  Kayser,* 
who  pointed  out  that  hydrogen  had  been  the  only  element, 
having  harmonically  related  lines,  which  had  possessed  only 
a  single  series  of  such  lines.  Kayser  and  Runge  had  pre- 
viously found  that  two  of  the  series  of  lines  of  an  element  end 
at  nearly  the  same  place.  On  examining  the  oscillation 
frequencies  of  the  new  lines,  Kayser  concluded  that  they  have 
this  characteristic,  and  constitute  a  new  hydrogen  series.  If 
these  lines  can  be  produced  in  laboratory  experiments,  im- 
portant information  as  to  stellar  temperatures  and  pressures  is 
likely  to  be  obtained. 

At  low  temperatures  wafer  vapor  gives  an  absorption- 
spectrum  rich  in  lines  which  are  chiefly  confined  to  the  red 
region;  these  constitute  a  large  number  of  the  terrestrial 
Fraunhofer  lines,  and  are  referred  to  under  nitrogen ;  they 
are  strongest  when  the  sun  is  low  in  the  horizon,  as  its  rays 
have  then  to  traverse  a  considerable  layer  of  the  atmosphere. 
When  the  latter  is  saturated  with  moisture,  a  "  rain-band  " 
is  visible  with  the  help  of  a  spectroscope  of  low  dispersive 

1  Bull.  Acad.  St.  Petersb.  (1880)   11,  307;    (1884!   12,    203.     Mem.    Acad. 
St.  Petersb.  (1882)  30,  No.  7;  (1883)  31,  No.  14.     W.   A.    15,  45.     See  also* 
H.  C.  Vogel,  P.  A.  (1872)  146,  569.     Wtillner,    P.   A.    135,  497;    137,   337; 
144,  481.     W.  A.   14,  355.     Seabroke,  P.  M.   [4]  43,  155.     Balmer,  W.   A_ 
(1885)  25,  80. 

2  Astrophys.  J.  (1897)  5,  92.     Science  (1897)  5,  726. 
8  Astrophys.  J.  (1897)  5,  95.     Science  (1897)  5,  726. 


1 30  SPEL'TR UM  ANA L  YSIS. 

power:  it  consists  of  bands  composed  of  water- vapor  lines, 
and  situated  between  the  red  end  and  the  ZMine.  The 
presence  of  the  rain-band  has  been  used  by  Piazzi-Smyth,1 
Capron,2  Grace  and  others  as  a  means  of  prognosticating  rain. 

Janssen 8  investigated  the  absorption-spectrum  of  steam 
contained  in  long  tubes  under  considerable  pressure,  and 
Schonn4  states  that  pure  water  exhibits  an  absorption-band. 
An  emission-spectrum  consisting  of  numerous  lines  in  the 
ultra-violet  is  obtained  by  burning  hydrogen  in  air,  or  passing 
it  through  the  electric  arc;  it  has  been  measured  by  Huggins, 
and  also  by  Liveing  and  Dewar,5  who  distinguished  five  series 
of  lines.  The  first,  between  wave-length  3268.2  and  3063.7, 
contains  about  1 16  lines;  the  second,  from  3057  to  2812, 
comprises  180  lines;  the  third,  from  2807  to  2609,  contains 
141  lines;  the  fourth  series,  from  2606  to  2450,  has  88  lines; 
and  the  fifth  series  includes  79  lines  between  wave-length 
2449  and  2268. 

Elementary  line-spectrum: 
[C  or  Ha]  6563.04   [F  or  H/J]  4861.49   [G  or  H^]  4340.66  [h  or  US]  4101.85 


[H]  3970.25                 [«]38S9.i5 
[<5]  3770.  7                   [e]  3752.05 
[o]  37II-9  (Ames). 

m  3835.5 

[C]  3  734-  1  5 

M  3798.0 

[77]  372  1.  S 

Compound  line-spectrum: 

6135-5 
5938.9 
5013-15 

6121.9 
5931-8 
4973-3 

6081.  o        6070.7 

5888.9        5884.5 
4934.5        4928.8 

6032.1 
5813.0 
4861.49 

6018.5 
5084.9 
4719.2 

5975.8 

5055.  *2 

4683.95 

1  N.  26,  551. 

2  The  Observatory,  1882,  pp.  42,  71. 

3  C.  r.  63,  289. 

4  P.  A.  Suppl.  Bd.  (1878)  9,  670.     W.  A.  6,  267.     See  also  for  the  spec, 
trum  of  water  Huggins,  P.  R.  S.  30,  576.     C.  r.    (1872)   74,    1050.     Liveing 
and  Dewar,  P.  R.  S.   30,   580;    33,  274.     P.   T.   (1888)  179,   2.     Lecoq  de 
Boisbaudran,    C.    r.    74,    1050.      Deslandres,    A.   c.    p.    (1888)   [6]    14,   257. 
C.  r.  100,  854.     Absorption  spectrum,  Janssen,  C.  r.  54,  1280;  56,  538;  60, 
213.     Russell  and  Lapraik,  N.  (1880)  22,  368.     Soret  and  Sarasin,   Arch. 
Sc.  phys.  et  nat.  (1884)  11,  327.     C.  r.  98,  624.     Ewan,  P.  R.  S.  (1895)  57, 
126. 

6  P.  R.  S.  35,  74. 


SPECTRA    OF   THE   ELEMENTS. 


4634.15  4461.1 

4177.25  4I7L35 

3990.15  3970.25 

3796.8  3684.3 


4412.35      434066      4212.65 
4101.85      4079.0        4069.75 
3889.15      3871-8        3863.3 
3674.5  (Hasselberg,  Ames). 

INDIUM. 


4205.2  4195-9 
4067.0  4062.6 
3835.6  3804.9 


This  element  was  discovered  in  1864  by  Reich  and 
Richter '  by  means  of  its  flame-spectrum,  which  consists  of 
an  indigo-blue  and  a  violet  line.  The  visible  portion  of  the 
spark-spectrum  has  been  measured  by  Clayden  and  Heycock,2 
and  a  small  part  of  it  also  by  Thalen,3  whilst  Hartley  and 
Adeney4  investigated  the  ultra-violet  region.  The  arc-spec- 
trum has  been  examined  by  Liveing  and  Dewar;6  it  contains 
only  the  two  lines  above  mentioned,  which  were  accurately 
measured  by  Kayser  and  Runge.8  Indium  furnishes  a 
remarkable  example  of  the  simplicity  of  the  arc-spectrum  as 
compared  with  that  of  the  spark;  the  latter  contains  numerous 
lines  both  in  the  visible  and  ultra-violet  regions  which  are 
absent  from  the  former. 

Flame-spectrum7 : 

4511.44          4101.87 

Arc-spectrum : 


4511.44     4101.87 
2932.71     2753-97 
2560.25     2521.45 

3258.66 
2714.05 
2460.  14 

3256.  17     303946. 
2710.38      2601.84 
2389.64      2340.30 

Spark-spectrum: 

6907.6 

6193.9 

6096.0 

5821.0 

5645.0 

5251.0 

4680.9 

4656.9 

4638.8 

4532.8 

4511.44 

4253.7 

4101.87 

4072.3 

4064.2 

4033-4 

3853.5 

3835.3 

3258.66 

3256.17 

3039.46 

2932.71 

2890.2 

2710.38 

2560.25 

2527-5 

2521.45 

2460.14 

2389.64 

235T.7 

2306.8 

J.  pr.  Chem.  89,  441. 
P.  M.  (1876)  5,  387. 
N.  A.  S.  U.  (1868)  [3]  6. 
P.  T.  (1883)  176,  63. 
P.  R.  S.  (1879)  28,  367. 
A.  B.  A.  1892. 

Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris,  1874).    Mtlller,  P.  A. 
124,  637. 


132  SPECTRUM  ANALYSIS. 


IODINE. 

The  more  important  investigations  of  the  line-spectrum  of 
iodine  are  those  of  Pliicker  and  Hittorf,1  and  of  Salet;2  the 
latter  passed  sparks  from  Leyden  jars,  or  a  Holtz  machine, 
through  a  Geissler  tube  containing  iodine:  the  tube  was  not 
closed  until  the  iodine  vaporized.  There  are  no  new  deter- 
minations. The  spectrum  obtained  with  a  condenser  in  the 
circuit  differs  from  that  produced  by  the  continuous  dis- 
charge.3 The  violet  iodine  vapors  produce  an  absorption- 
spectrum  extending  over  the  red  and  green,  but  not  over  the 
blue  and  violet  regions;  it  consists  of  numerous  slender  lines 
grouped  into  bands,  and  has  been  accurately  measured  by 
Hasselberg.4  H.  W.  Vogel 6  has  examined  the  absorption- 
spectra  of  various  solutions  of  iodine,  whilst  Gernez  *  has 
studied  those  of  iodine  chloride  and  iodine  bromide.  The 
rule  that  the  coefficient  of  extinction  of  solutions  of  a  colored 
substance  changes  with  the  concentration,  is  found  by 
E.  Thiele7  not  to  apply  to  iodine;  he  investigated  the 
absorption-spectrum  of  solutions  of  varying  strength  in  the 
same  solvent.  .  Previous  exceptions  to  this  rule  had  all  been 
electrolytes,  and  their  abnormal  behavior  had  been  thought 
to  be  due  to  electrolytic  dissociation,  but  iodine  is  a  non- 
electrolyte. 

1  P.  T.  155,  24. 

2  Spectroscopie  (Paris,  1888).    C.  r.  74,  1249;  75,  76.    A.  c.  p.  [4]  28,  29. 
See  also  Pliicker,  P.  A.   (1859)   107,    638.      Ciamician,   Wien.    Ber.   [2]  78, 
877.     Wullner,  P.  A.  120,  158.     Mitscherlich,  P.  A.  121,  474. 

3  Trowbridge  and  Richards,  .Amer.  Jour.  Sci.   (1897)  [4]  3,  117.     P.   M. 
43,  135. 

4  Mem.    de    1'Acad.    St.  Petersb.   (1888)  [7]  36.     See  also    Daniell  and 
Miller,  P.  A.  28,  386.     Morghen,  Beiblatter,   8,   822.     Thalen,    Le  spectre 
d'Absorption  de  la  vapeur  d'lode  (Upsal,  1869). 

6  Ber.  11,  919.     Monatsber.  Berl.  Akad.  1878,  p.  417. 
•  C.  r.  74,  466. 

7  Zeitschr.  phys.  Chem.  16,  147.     Ber.  28,  R  720. 


SPECTRA    OF   THE  ELEMENTS. 


133 


Spark-spectrum : 

6258   6211   6126   6079   5953  (5791   5774   5761   5739   5712) 
(5689   5674)  5625  (5495   5462   5534   5404)  (5345   5337)  5244 
5163   5016   4866  (4678   4669)  4634 

Absorption-spectrum  of  iodine  vapor: 


Group 

Group 
Group 
Group 
Group 
Group 

6316  —  6272  : 

6272—6234  : 
6234  —  6191  : 
6191  —  6149  : 
6149—6111  : 
6m  —  6069  : 

6316.51 
6291.94 

6253.07 

6233.93 
6190.97 
6111.25 
6108.87 

6298.29 
6291.46 
6252.96 
6229.68 
6153.08 

6069.31 

6297. 
6289. 
6237. 
6212. 
6149. 

76 
83 
72 
4i 

48 

6294. 
6272. 

6210. 

75 
42 

18 

6294.25 
6191.87 

Group 

6069  —  6031  : 

6063. 

49 

6047. 

82 

6046. 

87 

6045. 

94 

6042.81 

6035. 

82 

6034. 

83 

b  (6033. 

40 

6033. 

05) 

b  (6031 

.92 

6031. 

58) 

Group 

6031—5992  : 

6030.99 

6024. 

38 

6020. 

38 

6018. 

37 

6008.85 

(5994- 

65 

5994- 

^2) 

5993- 

89 

5993- 

03 

Group 

5992—5976  : 

Group 

5955—5917  : 

(5948.83 

5948. 

62) 

b(5922. 

53 

5922. 

04) 

b(592i 

•77 

5921. 

24) 

5(5921. 

00 

5920. 

58) 

5920.00 

5919 

•75 

59I9- 

36 

59i9- 

II 

5917. 

55 

Group 

5917—5881  : 

5885. 

00 

5884. 

74 

5884. 

10 

5881. 

17 

Group 

5881—5846  : 

5866. 

9i 

5859- 

85 

5856. 

49 

(5850. 

5i 

5850 

.22) 

5848.57 

5847-08 

5846. 

54 

5846. 

22 

Group 

5846—5811  : 

5815- 

40 

5812. 

66 

5811. 

65 

Group 

5811—5778: 

(5805. 

86 

5805. 

63) 

(5798. 

69 

5798. 

45) 

(5798 

.14 

5797- 

93) 

5793- 

47 

5778. 

87 

5778. 

62 

5778 

.28 

Group 

5778—5746  : 

5746. 

21 

Group 

5746—5715  : 

5745- 

92 

5720. 

60 

5715. 

45 

Group 

5715—5684: 

57I4- 

92 

5712. 

24 

5708. 

38 

5698. 

70 

5697 

.84 

5693- 

05 

5685. 

09 

5684.54 

Group 

5684—5655  : 

5683. 

08 

5678. 

59 

5676. 

82 

5658. 

98 

Group 

5655—5626  : 

5654. 

71 

5649- 

61 

5647. 

68 

5646. 

72 

b(5646 

.14 

5645- 

50) 

5640. 

90 

5640.00 

5639- 

15 

b(5638 

.64 

5638. 

23) 

5637- 

36 

(5628. 

90 

5628. 

35) 

5627.97 

5627. 

19 

5626. 

50 

Group 

5626—5599  : 

(5620. 

59 

5620. 

33) 

5616. 

50 

5614. 

53 

5602 

.98 

5601. 

8r 

5699' 

14 

Group 

5599—5587: 

5588. 

98 

5587.56 

Group 

5587—5560  : 

5585. 

10 

(5577. 

63 

5577- 

42) 

5574- 

ii 

5572 

•71 

556i. 

58 

556o. 

44 

556o. 

25 

5559- 

57 

Group 

5560—5533  : 

5557- 

17 

5553- 

61 

5549- 

40 

b(5547. 

92 

5546 

.96 

5546.07) 

5545. 

•57 

5542. 

37 

5540.91 

5533 

•37 

134 

Group 

SPECTRUM  ANALYSIS. 
5533—  5507:b(553i-75         553i-io)        5527-58 

5526.38     b(5522. 

25 

5521.79) 

5521. 

•34 

5520. 

33 

Group 

5507—5482  : 

5505. 

19 

5504. 

95 

55oo. 

43 

5498. 

32 

5497. 

81 

(5497- 

51         5497-15) 

5496. 

36 

5490. 

37 

5489- 

67 

5488. 

95 

0(5483.00 

5482. 

n) 

Group 

5482—5457  : 

5473-55 

b(5473- 

12 

5472. 

67) 

5468. 

38 

5466. 

76 

(5457- 

90 

5457-08) 

Group 

5457—5434  : 

5438- 

43, 

5434-03 

Group 

5434—5411  : 

5430.71 

5425. 

76 

54I9- 

78 

54io- 

85 

5416. 

99 

54I4- 

28 

5412 

31 

541'- 

66 

Group 

5411—5389: 

b  5410.75 

5404- 

96 

5404.04 

b(5393- 

91 

5393- 

44) 

5390. 

85 

b  (5390.  21 

5389. 

01) 

Group 

5389—5367  : 

538i. 

90 

538o. 

93 

5378. 

05 

5377- 

32 

5375- 

20 

5374- 

38 

5369- 

74 

5369- 

20 

5368. 

5i 

5368. 

01 

Group 

5367—5347  : 

5364. 

76 

5358. 

81 

5357- 

91 

5356. 

63 

5355- 

89 

5353- 

28 

5350. 

56 

5349- 

87 

5348.06 

5347- 

35 

Group 

5347—5327  : 

5346. 

24 

5343- 

12 

5341- 

43 

5340. 

14 

5333- 

73 

5333- 

10 

5330.97 

5329. 

32 

Group 

5327—5308  : 

Group 

5308—5291  : 

Group 

5291—5273  : 

5290.72 

Group 

5273—5255  : 

5272. 

75 

Group 

5255—5240  : 

Group 

5240—5224  : 

5224. 

10 

Group 

5224—5209  : 

5215- 

83 

5209.46 

Group 

5209-5195  : 

5195. 

22 

Group 

5195—5182: 

Group 

5182  —  5168  : 

5181. 

96 

5168. 

65 

Group 

5168—5156: 

5161. 

45 

5156. 

16 

Group 

5156—5145  : 

5144- 

71 

IRIDIUM. 

There  are  no  accurate  measurements  of  the  spectrum  of 
this  element.  Kirchhoff  1  observed  three  faint  lines  of  w—lt 
6348.1,  545O>6»  and  5300  6,  and  Lockyer2  has  measured  six 
in  the  arc-spectrum  between  wave-length  4000  and  3900. 
H.  W.  Vogel 3  has  described  the  absorption-spectrum  of 
ammonium  iridio-chloride. 

Arc-spectrum : 
3992  2       3976.0 


3945- 


3934-7 


3915.2 


3902.5 


1  A.  B.  A.  1861. 


2  P.  T.  1881,  Pt.  3. 


8  Prakt.  Spectralanal.  (Berlin,  1889). 


SPECTRA    OF   THE  ELEMENTS.  13$ 


IRON. 

The  spectrum  of  iron  is  the  richest  in  lines;  they  are  dis- 
tributed over  every  part  of  the  field,  and  therefore,  like  the 
Fraunhofer  lines,  are  excellently  adapted  for  purposes  of 
orientation  in  spectroscopic  observations.  Omitting  the 
older  and  less  accurate  measurements,  the  following  investi- 
gations are  of  greatest  importance  :  Thalen  '  made  a  careful 
comparison  of  the  lines  in  the  iron-carbon  arc  with  those  of 
the  solar  spectrum  shown  in  the  atlases  of  Angstrom,  and  of 
Fievez  and  Vogel,  and  investigated  those  between  760^  and 
4OO,w/u.  In  the  ultra-violet  Cornu  '  photographed  the  more 
prominent  lines  between  4iOju/w  and  295^,  and  Liveing 
and  Devvar3  caiefully  extended  this  work  to  the  region 
between  295;^  and  230^^;  they  also,  as  did  Hartley  and 
Adeney,4  investigated  the  spark-spectrum  of  iron.  All  these 
measurements  were  based  on  Angstrom's  erroneous  determi- 
nation of  the  wave-length  of  the  ZMine,  so  that  a  reinvestiga- 
tion  of  the  subject  was  very  desirable.  Kayser  and  Runge  * 
undertook  this  task,  and  usually  attained  an  accuracy  of  0.02 
Angstroms;  they  measured  more  than  4500  lines,  and  on 
comparing  them  with  Rowland's  solar  atlas  between  520^^ 
and  320;.^,  they  were  unable  with  certainty  to  detect  a  single 
line  which  does  not  appear  in  the  solar-spectrum.  The 
absrption-spectra  of  solutions  of  various  compounds  of  iron 
are  not  specially  characteristic;  they  have  been  studied  by 

N.  A.  S.  U.  [3]  6.      Le  spectre  du  fer.  1884. 

Spectre  normal  du  soleil  (Paris,  1881). 

P.  T.  174,  210.      P.  R.  S.  32,  402. 

P.  T.  1884. 

A.  B.  A.  1888,  1890.  See  also  Huggins,  P.  T.  (1864)  154,  139.  'Kirch- 
hoff,  A.  B.  A.  1861.  Angstrom,  Recherches  sur  le  spectre  solaire,  1868. 
Mascart,  Ann.  de  1'ecole  normale  (1866),  4.  Secchi.  C.  r.  (1873)  77,  173. 
Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris,  1874).  Lockyer,  P.  T.. 
164,  479.  H.  W.  Vogel,  Prakt.  Spectralanal.  (Berlin,  1889). 


UNIVERSITY 


136  SPECTRUM  ANALYSIS. 

H.  W.  Vogel,1  and  are  referred  to  in  the  following  chapter. 
Roscoe,"  Lielegg,3  Marshall  Watts,4  and  others  have  investi- 
gated the  spectrum  of  the  flame  observed  during  the  manu- 
facture of  steel  by  the  Bessemer  process,  and  more  recently  it 
has  been  thoroughly  examined  by  Hartley.5  Watts  believed 
that  the  green  bands  are  produced  by  manganese  oxide,  and 
that  their  disappearance  marks  the  instant  when  the  iron  is 
completely  decarbonized,  and  the  blast  of  air  should  be 
stopped.  Before  the  application  of  the  spectroscope  for 
this  purpose  it  was  exceedingly  difficult  to  determine  the 
precise  moment,  since- experience  was  the  sole  guide  and  often 
proved  untrustworthy. 

Hartley's  exact  investigations  have  shown  that  the 
phenomena  of  the  Bessemer  flame  is  much  more  complex 
than  was  previously  divined.  This  is  owing  to  the  super- 
position of  bands  of  manganese,  carbon,  carbonic  oxide,  and 
possibly  also  of  those  of  manganese  oxide,  and  of  the  lines  of 
iron,  manganese,  potassium,  sodium,  lithium,  and  hydrogen. 
The  bands  of  manganese  are  to  some  extent  obscured  by  the 
strong  continuous  spectrum  of  the  carbonic  oxide  flame,  and 
by  the  bands  of  carbon. 

The  cause  of  the  nonappearance  of  the  lines  in  the  spec- 
trum at  the  beginning  of  the  "  blow  "  is  the  comparatively  low 
temperature  at  this  period,  and  the  free  oxygen,  which 
escapes  with  carbon  dioxide,  giving  a  gaseous  mixture  con- 

1  Ber.  (1875)  8,  1537.     See  also  Miiller,  P.  A.    (1847)   72,   67.      Ewan,  P. 
K.  S.  (1895)  57,  140. 

2  P.  M.  P.  S.  1863. 

3  Sitzungsber.  Wien.  Akad.  1867. 

4  P.  M.  [4]  34,  437;  38,  249- 

5  P.  T.  (1894)  185,  1041.      P.  R.  S.  (1895)  59,  98.    Journ.  Iron  and  Steel 
Inst.  (1895)  No.  TI.    See  also  Kohn,  Dingier  polyt.  J.  (1864)  175,  296.  Silli- 
man,  P.  M.  41,  i.     Tunner,  Dingier  polyt.   J.   (1865)   178,  465.      Brunner, 
Oester.  Zeitschr.  fvirBerg-und  Hiittenwesen  (1868),  16,  226.   Kuppelwieser, 
Ibid.  (1868)    16,    59.     v.    Lichtenfels,   Dingl.    polyt.    J.    191,   213.      Spear 
Parker,  C.  N.  23,  25.     Wedding,    Zeitschr.  f.   Berg-.  Hiitten-  und  Salinen- 
wesen  (1869),  27,  117.     Greiner,  Revue  universelle  (1874),  35,  623. 


SPECTRA    OF   THE  ELEMENTS. 


137 


taining  too  small  a  proportion  of  carbonic  oxide  to  produce 
luminosity.  During  the  "  boil  "  the  luminosity  of  the  flame 
is  due  to  the  combustion  of  highly  heated  carbonic  oxide, 
and  also  to  the  presence  of  the  vapors  of  iron  and  manganese. 
The  disappearance  of  the  manganese-spectrum  at  the  end  of 
the  "  fining  "  stage  is  primarily  caused  by  the  carbonic  oxide, 
which  escapes  from  the  converter,  being  reduced  in  quantity 
owing  to  the  diminished  supply  of  carbon  in  the  metal. 
When  the  last  traces  of  carbon  are  gone,  so  that  air  can 
escape  through  the  metal,  the  blast  instantly  oxidizes  any 
manganese,  either  in  the  metal  or  in  the  atmosphere  of  the 
converter,  and  also  some  of  the  iron.  The  temperature  must 
then  fall  with  great  rapidity. 
Arc-spectrum : 


6678.23 

6663.38 

6633.92 

6609.35 

6594-11 

6593.14 

6575.17 

6569.46 

6546.47 

6518.62 

6495.20 

6431.06 

6421.55 

6420.17 

6411.86 

6408.23 

6400.27 

6393-81 

6380.95 

6337.07 

6335.55 

6322.91 

6318.22 

6302.73 

6301.71 

6297.99 

6291.18 

6270.44 

6265.34 

6256.57 

6254.45 

6252.76 

6246.53 

6232.90 

6230.94 

6219.49 

6215.36 

6213.63 

6200.53 

6191.77 

6180.42 

6170.69 

6157.96 

6141.93 

6137.91 

6136  85 

6128.11 

6103.45 

6102.40 

6078.71 

6065.71 

6056.21 

6042.31 

6027.27 

6024.28 

6020.35 

6008.78 

6003.28 

5987.29 

5985-04 

5983.9? 

5977.12 

5975-58 

5956.92 

5953-ot 

5934.83 

5930.29 

5916.47 

5914.38 

-905.94 

5862.58 

5859.91 

5816.59 

5782.35 

5775.30 

5763.22 

5753-33 

5731.98 

5718.10 

5709.61 

5701-77 

5686.66 

5662.75 

5659  06 

5638.52 

5624.77 

5615.88 

5603.17 

558699 

5576.32 

5573.07 

5569.85 

5565-83 

5555-03 

=  506.98 

5501.69 

5497-70 

5476.89 

5474-13 

5463-49 

5455.83 

5447.16 

5445.28 

5434-74 

5429.81 

5424.23 

5415.42 

5411.20 

5405.99 

5404.42 

5400.67 

5397.32 

5393.38 

5383  58 

5371.67 

5370.17 

5367-67 

5365.08 

5353-59 

5341.21 

s-uo.  16 

5333-09 

5328.71 

5328.21 

5324.37 

5307-54 

5302.52 

5283.80 

5281.97 

5273.55 

5270.52 

[E2]5269.72 

5266.73 

5263.42 

5250.81 

5242.66 

5233.12 

5230.01 

5227.39 

5227.08 

5216.43 

5208.80 

5202.48 

5195.09 

5192.53 

5191.68 

5I7L78 

5169.07 

5167.57 

5162.45 

5153-34 

5151-02 

?T48.42 

5139.65 

5139.44 

5137.56 

5133.70 

5125.30 

5123.88 

5110-57 

5107.82 

5105.73 

J38 


SPECTRUM  ANALYSIS. 


5098.83 

5083.  50 

5079.91 

5079.42 

5068.95 

5065.15 

5051.78 

5050.01 

5041.91 

5015-13 

5012.21 

5006.30 

5005.90 

5002.08 

4982.73 

4966.  29 

4957-50 

4957.48 

4938.99 

4920.68 

4919.19 

4891.68 

4890.94 

4878.41 

4872.31 

4871.49 

4859.94 

4789.80 

4737.00 

4707.51 

4691.59 

4679.03 

4668.36 

4667.62 

4654.76 

4647.60 

4638.19 

4637.68 

4625.25 

4619.46 

4611.47 

4607.85 

4603.09 

4598.32 

4592.82 

4556.28 

4548.01 

453L3I 

4538.84 

4525.32 

4494-  74 

4484.42 

4482.40 

4476.25 

4469.58 

4466.75 

4461.83 

4459-29 

4454-55 

4447.90 

4443-35 

4442.52 

4433.37 

4430.79 

4427.49 

4422.74 

4415  30 

4408.59 

4407.85 

4404.94 

4401.51 

4391.14 

4388.62 

[d]4383.72 

4376.10 

4369.94 

4367.73 

4352.90 

4337.20 

[f]4325  94 

4315.23 

4309.55 

[G  14308.  07 

4305-63 

4299.44 

4294.31 

4285.62 

4282.54 

4271  92 

4271  35 

4268.02 

4260.67 

4250.96 

4250.30 

4247.65 

4245.40 

4239'95 

4239.03 

4236.14 

4233.81 

4227.65 

4225.66 

4224.32 

4222.39 

4219.52 

4217.74 

4216.33 

4210.53 

4204.  12 

4202.18 

4199.26 

4198.47 

4196.36 

4I95-5I 

4191.62 

4187.97 

4187.22 

4185.06 

4182.51 

4181.91 

4177.71 

4176.67 

4175.76 

4175.03 

4172.86 

4172.25 

4171.04 

4158.94 

4I57.95 

4156.93 

4i55.oo 

4154-62 

4154.09 

4149.49 

4147.79 

4144.01 

4143.58 

4137-11 

4134.82 

4133-01 

4132.20 

4127.73 

4122.64 

4121.97 

4118.72 

4114.60 

4109.93 

4107-65 

4104.25 

4100.88 

4098-31 

4096.  1  1 

4085.43 

4085.12 

4084.64 

4079.96 

4078.46 

4076.77 

4074.92 

4071.90 

4070.90 

4068.12 

4067.41 

4067.09 

4063.75 

4062.60 

4057.96 

4045.97 

4034.64 

4033.21 

4030.89 

4022.02 

4014.68 

4009.85 

4005.31 

3998.22 

3997-54 

3986.32 

3984.08 

3981.91 

3977-90 

3971.48 

3969.39 

3956.82 

3952.76 

3951.30 

3950.10 

3948.92 

3942.58 

3941.03 

3935-97 

3933.80 

3930-37 

3928.06 

3923.05 

3920.41 

39I7.34 

3916.88 

3906.63 

3904-05 

3903-11 

3899.85 

3898.10 

3895.80 

3888.68 

3887.22 

3878.71 

3886.42 

3878.17 

3873.93 

3872.66 

3867.38 

3865.70 

3860.04 

3859-39 

3856.52 

3852.76 

3851.01 

3850.16 

3847.01 

3843-41 

3841.24 

3840.58 

3839-43 

3836.53 

3834.42 

3827.97 

3826.02 

3824.63 

[L]3820.56 

3815.98 

3813.17 

3806.89 

3805.49 

3799.70 

3798.66 

3797.70 

3795-15 

3790.27 

3788.03 

3779-63 

3767.33  . 

3765.71 

3763.94 

3758.38 

3749-62 

3748.41 

3746.05 

3745-71 

3743-51 

373?.48 

3737.26 

3735.49 

,.3735.oi 

3732.55 

[M](3727.77 

3727.17) 

3724-b5 

3722.69 

3720.05 

3716.59 

3709.37 

3708.07 

3704-63 

3701.24 

3694.17 

3687.81 

3687.62 

3686.14 

3082.39 

SPECTRA    OF   THE   ELEMENTS. 


139 


3669.69 

3659-64 

3651.65 

3647.95 

3640.57 

3631-59 

3623  37 

3622.19 

3621.65 

3618.89 

3617-98 

3610.33 

3609.03 

3606.87 

3605.66 

3594-75 

3587.14 

3586.24 

3584.82 

[N]358i.34 

3574.04 

3572.16 

3570.23 

3565.53 

3553.69 

3557-03 

3555-08 

3545.78 

3542.24 

3241.20 

3536.69 

3533-34 

3527-94 

3526.55 

3526.29 

3521.40 

3513.97 

3497-99 

3497-27 

3490.72 

3489.78 

3476.85 

3475  56 

3471-44 

3465.97 

3460.06 

3452-39 

3452.03 

3450.44 

3447-41 

3445.26 

3444.02 

[OJ3441.13 

3440.70 

3428.30 

3427-24 

3426.75 

3426.48 

3425-12 

3424.40 

3422.73 

3418.61 

3417.96 

3415.65 

3413.26 

3410.30 

3407.57 

3406.96 

3404.44 

3402.37 

3401.64 

3399.43 

3394-69 

3392.76 

3384-07 

3380.21 

3379-15 

3378.78 

337091 

3369-66 

3366.92 

3355-33 

3348.03 

3342.39 

3340.68 

3337-77 

3329-04 

332388 

3314.87 

3310.57 

3307.37 

3306.48 

3306.10 

3298.24 

3292-74 

3292.17 

3291.14 

[QJ3286.87 

3280.41 

3274.09 

3271-11 

3265.72 

3257.73 

3254-5I 

3251.32 

3248.35 

3244.31 

3239.54 

3234-II 

3231.07 

3227.92 

3225.91 

3222.16 

3219-91 

3219-70 

32I7.53 

3216.07 

3214.14 

3212.12 

3205.49 

3200.58 

3199.66 

3197-08 

3T93.4I 

3192-89 

3191.81 

[RJ318034 

3178.12 

3175.54 

3171-48 

3166.59 

3166.01 

3162.08 

3160.74 

3158.03 

3I57.I9 

3153.35 

3151-42 

3I44.IO 

3142.58 

3I34.25 

3132.65 

3126.29 

3125.76 

3119.62 

3116.73 

3102.80 

3100.78 

[S2]3ioo.42 

3100.06 

3098.29 

3093.96 

3091.71 

3083  84 

3075.82 

3067.35 

3059.23 

3057.54 

3055.39 

3053.I7 

[s]3047.70 

3045.20 

3042.79 

3042.17 

3041-87 

3040.58 

3037.49 

3037.41 

3031.78 

3031.35 

3030.28 

3026.61 

3025.96 

3024.15 

[T](302i.i9 

3020.76) 

3019.09 

3017-75 

3016.29 

3011.61 

3009.70 

3008.23 

3007.34 

3003.18 

3001.04 

3000.  60 

2999.63 

[t]2991.52 

2991.82 

2990.48 

2987.40 

2985.69 

2984.96 

2983.67 

2981.99 

2981.57 

2980.66 

2976.23 

2973.36 

2973-25 

2970.22 

2969.56 

2967.00 

2965.38 

2960.11 

2957.61 

2957.48 

2957.42 

2954.06 

2953-90 

2953.61 

2950.38 

2949.32 

2948.56 

[U]2947.99 

2947..°  i 

2944-53 

2941.46 

2937-94 

2937.02 

2929.13 

2926.69 

2925.47 

2923-96 

2923.43 

2920.79 

2918.14 

2914.37 

2912.27 

2909.60 

2909.00 

2907.60 

2902.05 

2901.48 

2899.52 

2898.55 

2895.14 

2894.60 

2892.59 

2887.91 

2886,41 

2883.82 

2881.68 

2880.87 

2877.40 

2874.27 

2872.41 

2869.41 

2866.71 

2863.95 

2863.48 

2862.59 

2858.99 

2853.84 

2852.22 

2851.89 

2850.72 

2848.80 

2846.90 

2845.66 

2844.08 

2843.74 

2840.53 

2840.09 

2838.23 

2835-54 

2832.53 

2828.90 

2825.78 

2825.67 

140 


SPECTRUM  ANALYSIS. 


2824.45 

2823.37 

2819.38 

2817.58 

2815.61 

2813.39 

2808.40 

2807.08 

2804.59 

2803.71 

2801.18 

2798  36 

2797.85 

2795-61 

2795.03 

2794.80 

2792.47 

2791.87 

2791.54 

2789.90 

2788.20 

2788.08 

2783-78 

2781.95 

2779.37 

2778.92 

2778-32 

2778.18 

2774.79 

2773.3I 

2772.21 

2769.40 

2767.62 

2767.02 

2764.44 

2763.20 

2762.85 

2762.11 

2761.88 

2760.99 

2759.89 

2757.94 

2757.41 

2756.43 

2755.83 

2754.51 

2754.12 

2753.77 

2753.40 

2750.98 

2750.24 

2749.64 

2749-45 

2749.26 

2747.67 

2747.08 

2746.57 

2745-16 

2744.63 

2744.16 

2743.66 

2743.26 

2742.48 

2739.62 

2737.40 

2737.05 

2735.74 

2735.64 

2735.54 

2734.42 

2733.67 

2730.82 

2728.93 

2728.14 

2727.64 

2726.23 

2725  oo 

2723  67 

2720.99 

2720.31 

2719.54 

2719.12 

2718.54 

2714.51 

2711.74 

2710.64 

2708.67 

2706.68 

2706.10 

2704.09 

2699.21 

2697.11 

2696.44 

2696.15 

2690.15 

2689.95 

2689.31 

2680.56 

2679.16 

2673.31 

2669.60 

2668.00 

2667.08 

2666.97 

2666.46 

2664.77 

2662.16 

2661.32 

2660.51 

2656.88 

2656.24 

2651.81 

2647.67 

2645-55 

2644.08 

2641.77 

2635.90 

2631.40 

2631.12 

2628.39 

2625.75 

2623.61 

2621.75 

2620.50 

2617.70 

2615.53 

2613.94 

2611.96 

2607.19 

2605.80 

2604.93 

2599.49 

2598.46 

2594.23 

2593-78 

2591.64 

2588.14 

2585.95 

2584-63 

2582.53 

2579-95 

2578.04 

2576.77 

2576.23 

2575.86 

2574.46 

2572.85 

2570.59 

2569.76 

2566.99 

2563.56 

2562.61 

2560.68 

2556.95 

2556.41 

2553-35 

2551.22 

2549.68 

2548.79 

2547.09 

2546.29 

2544-86 

2544.05 

2542.23 

2541.06 

2539.01 

2537.24 

2536.93 

2535.70 

2533.89 

2532.40 

2530.82 

2529.43 

2528.60 

2527.50 

2527.33 

2526.33 

2525-51 

2525.14 

2524-35 

2523-79 

2523.22 

2522.92 

2522.00 

2521.12 

2518.19 

2517.79 

2517.28 

2516.22 

2514-41 

2512.41 

2511.08 

2510.91 

2508.81 

2508.02 

2507.01 

2505.67 

250303 

2502.56 

2501.90 

2501.20 

2498.99 

2497.91 

2497-18 

2496.63 

2496.04 

2493.30 

2491.24 

2491.01 

2489.07 

2488.24 

2484.28 

2483.34 

2480.28 

2480.04 

2472.85 

2476.80 

2474.91 

2473-18 

2472.86 

2472.43 

2469.00 

2467.83 

2466.84 

2465.23 

2462.74 

2461.31 

2460.40 

2458.81 

2457.68 

2453.56 

2447.84 

2444.61 

2443-97 

2442.65 

2440.  28 

2439.85 

2439.39 

2438.30 

2436.48 

2435.07 

2431-11 

2430.19 

2429.56 

2424.23 

2421.82 

2413.39 

2411.19 

2410.60 

2406.74 

2404.96 

2404.  5  1 

2399.31 

2395.72 

2391.56 

2388.73 

2384.51 

2383.27 

2382.12 

2380.85 

2379.41 

2375-33 

2373.82 

2370.59 

2368.69 

2366.69 

2364.91 

2362.14 

2360.40 

2360.09 

SPECTRA    OF   THE   ELEMENTS. 


2359.20 

2354.96 

2348.39 

2344.40 

2344.  1  2 

2343.56 

2338.11 

2332.86 

2331.41 

2327.45 

2320.43 

2313.20 

2309.08 

2303-55 

2298.25 

2297.88 

2293.98 

2291.21 

2289.06 

2230.13 

2227.81 

2214.70 

LANTHANUM. 

The  spark-spectrum  of  lanthanum  is  rich  in  lines  which 
have  been  measured  by  Kirchhoff,1  and  more  especially  by 
Thalen." 

Spark-spectrum: 

6393.5 
5770-0 
5376.5 
5123.0 
4330.5 
4217.0 


4042.5 


6250.0 

5974-0 

5930.0 

5805.5 

5795-0 

579L5 

5788.0 

5674.0 

5632.0 

5588.0 

5501.5 

5455-5 

538i.o 

5381.5 

5340.5 

5303-5 

5302.8 

5302.0 

5188.5 

5183.5 

517^0 

4526.5 

4525-0 

4523.0 

4431.0 

4428.0 

4385-0 

4383 

4322.5 

4295.5 

4286.5 

4268.5 

4263.5 

4238.5 

4235.5 

4196.5 

4192.0 

4152.0 

4142.5 

4122.0 

4086.5 

4077.0 

403L5 

3947-0 

LEAD. 


The  arc-spectrum  is  obtained  by  the  use  of  leaden  elec- 
trodes, preferably  in  an  atmosphere  of  hydrogen,  so  as  to 
avoid  the  production  of  the  oxide  bands  which  were  observed 
by  Plucker  and  Hittorf 3  on  passing  sparks  through  a  Geissler 
tube  containing  lead  chloride  vapor.  The  arc-spectrum  differs 
materially  from  that  of  the  spark;  it  has  been  investigated 
by  Liveing  and  Dewar,4  and  more  recently  by  Kayser  and 
Runge.5  Lockyer  and  Roberts8  observed  that,  at  low  tem- 
peratures, lead  vapor  produces  an  absorption-spectrum  in  the 
red  and  blue.  All  lead  compounds  exhibit  the  channelled 
oxide-spectrum  consisting  of  the  bands  of  \  —  5905,  5685, 
5611,  and  5461;  they  shade  off  towards  the  red,  and  have 
been  described  by  Mitscherlich,7  Plucker  and  Hittorf,  and 


A.  B.  A.  1861. 

Konffl.   Svenska  Vetensk.  Akad.    Handl.    (1874)  12,  No.  4.     See    also 
Bu   sen.  P.  A.  155,  366.     Cleve,  C.  r.  95,  33. 
P.  T.  155,  25. 

P.  R.  S.  (1879)  29,  402.      P.  T.  (1882)  174,  18-7. 
A.  B.  A.  1893. 

P.  R.  S.  23.  344.     Lockyer,  P.  T.  163,  253,  369. 
P.  A.  121,  468. 


142  SPECTRUM  ANALYSIS. 

Lecoq  de  Boisbaudran.1  In  the  Bunsen  flame  they  are  too 
fugitive  to  be  observed  with  certainty,  but  H.  W.  Vogel 2 
has  constructed  an  apparatus  which  permits  of  the  addition  of 
lead  chloride  vapor  to  a  hydrogen  or  coal-gas  flame,  and 
renders  them  much  more  permanent. 
Arc  and  spark  spectra: 

6657.4*  6453.3*  6041.2*  6002.08  5875-1*  5608.0*  5547-2* 
5373.4*  5201.65  5045-9*  5005.62  4387.3*  4246-6*  4057.97 
3740.10  368360  3639.71  3572.88  3262.47  3240.31  3220.68 
2873.40  2833.17  2823.28  2802.09  2697.72  2663.26  2650.77 
2614.26  2577.35  2476.48  2446.28  2443.92  2428.71  2411.80 
2402.04  2393.89  2332.54  2247.00  2237.52  2175.88  2170.07 
2115.1  2112.0  2088.5 

LITHIUM. 

Lithium  salts  are  dissociated  in  the  Bunsen  flame  and 
exhibit  two  lines  belonging  to  the  metal :  the  one,  A  =  6708.2, 
is  very  bright  and  deep  red;  the  other,  A  =  6103.8,  is  fainter 
and  orange-colored.  Other  lines  are  visible  in  the  spark  a'nd 
arc  spectra.  Kayser  and  Runge 3  measured  eighteen,  and 
Liveing  and  Dewar4  observed  two  additional  ones  in  the 
ultra-violet. 

Arc  and  spark  spectra: 

6708. 2f  6103. 77f  4972.11    4602.37  4132.44    3915.2    3232.77    2741.39 

MAGNESIUM. 

The  bibliography  shows  how  frequently  the  magnesium- 
spectrum  has  been  subjected  to  exhaustive  investigation;  it 

1  Spectres  lurnineux  (Paris,  1874). 

2  Prakt.    Spectralanal.  (Berlin,   1889).     See  also   Thalen,    N.    A.  S.   U. 
(1868)  [3]  6.     Kirchhoff,  A.  B.  A.  1861.     Huggins,  P.  T.  154,  139.     Hartley 
and  Adeney,  P.  T.  175,  163. 

3  A.  B.  A.  1890. 

4  P.  R.  S.  28,  367,  471  ;  (1880)  30,  93.     P.  T.  (1883)  174,  215.     See  also 
Kirchhoff  and  Bunsen,  P.  A.  110,  167.     Kirchhoff,  A.  B.  A.  1861.      Huggins, 
P.  T.  1864,    p.   139.     Miiller,  P.   A.   118,  641.     Ketteler,   P.   A.    104,  390. 
Wolf  and  Diacon,  C.  r.  55,  334.      Riihlmann,    P.  A.  132,  i.     Thalen,  N.  A. 
S.  U.  (1868)  [3]  6.      Lecoq  de  Boisbaudran,  Spectres  lurnineux  (Paris,  1874). 

*  Visible  only  in  the  spark-spectrum.     (Thalen.) 
f  Visible  also  in  the  flame-spectrum  of  lithium  salts. 


SPECTRA    OF   7^HE   ELEMENTS.  143 

is  obtained  by  burning  the  metal  in  air,  by  passing  sparks 
through  a  solution  of  a  magnesium  salt,  or  between  electrodes 
of  the  metal,  and  by  the  combustion  of  the  metal  ini  the 
carbon  arc.  Liveing  and  Dewar  1  examined  the  flame,  spark, 
and  carbon  arc  spectra  in  atmospheres  of  \arious  gases;  the 
spectra  are  identical,  although  the  lines  may  differ  in  bright- 
ness. They  also  observed  a  number  of  oxide  bands  of 
A  =  5006-4934  and  3865-3720;  these  shade  off  in  the  violet. 
A  band  between  A=  3634  and  3621  is  also  visible  in  the 
oxyhydrogen  flame.  They  sta'e  that  when  magnesium  is 
burnt  in  hydrogen  the  elements  combine,  and  the  resulting 
product  exhibits  a  band-spectrum  between  /I  =  5618  and 
4803.  Kayser  and  Runge2  have  made  more  recent  and 
accurate  measurements  of  the  arc-spectrum,  using  magnesium 
powder,  or  wire,  and  carbon  poles;  they  were  unable  to  detect 
the  bands  of  the  oxide  or  hydrogen  compound,  but  the  former 
were  plainly  visible  on  burning  the  metal  in  air.  E.  Becquerel 3 
found  the  infra-red  lines  A  =  8990,  10,470,  12,000,  and  12,120 
in  the  arc-spectrum.  Magnesium  compounds  are  not  dis- 
sociated in  the  Bunsen  flame. 
Spark  and  arc  spectra: 

5528.75  5183.84*  5172.87*  5i67-55*  47O3-33  4571-33*  4352.18 

3838.44  3832.46*  3329.51*  3336.83  3332.28  3330.08  3097.06 

3093.14  3091.18  2942.21  2938.67  2852.22*  2802.80  2795.63 

2783.08  2781.53  2779.94  2778.36  2776.80 

1  P.  R.  S.  28,  367  ;  30,  93  ;  32,  189.     P.  T.  (1883)  174.  208. 

9  A.  B.  A.  1891. 

3  C.  r.  96,  1218  ;  97,  72.  See  also  Kirchhoff,  A.  B.  A.  1861.  Thalen, 
N.  A.  S.  U.  (1868)  6.  Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris, 
1874).  Cornu,  Spectre  normal  du  soleil  (Paris,  1881).  Bunsen,  P.  A.  155, 
366.  Fievez, 'Bull,  de  1'Acad.  R.  de  Belgique  (1880),  [2]  1,  91.  Hartley 
and  Adeney,  P.  T.  (1884)  175,  95. 


*  Also  visible  in  the  flame-spectrum.     (Liveing  and  Dewar.) 


144  SPECTRUM  ANALYSIS. 

MAGNESIUM    HYDRIDE.1 

Bands  extending  towards  the  red: 

5619       5567       5514       5513       5512       5211       5181       4850      4804 
MAGNESIUM    OXIDE.1 

Bands  extending  towards  the  red : 

5001   4991   4981   4970 

MANGANESE. 

The  spark-spectrum  of  manganese  has  been  measured  by 
Huggins,'2  and  by  Thalen;3  the  arc-spectrum  by  Angstrom,* 
and  Thalen,  and  in  part  by  Lockyer,5  and  Cornu.'  The 
spectra  are  not  identical,  and  they  have  not  been  the  subject 
of  recent  investigation  except  by  Hartley,7  who  examined  the 
oxyhydrogen  flame-spectrum  of  manganese,  and  manganese 
oxide. 

Potassium  permanganate  exhibits  the  most  characteristic 
absorption-spectrum  of  any  manganese  compound;  it  has 
been  investigated  by  Gladstone,8  Brewster,9  and  H.  W. 
Vogel.10  The  last  states  that  the  spectra  of  the  solid  salt  and 
of  the  solution  are  similar,  but  not  identical;  the  spectrum 
of  potassium  manganate  is  quite  different  (comp.  following 
chapter).  The  determination  of  potassium  permanganate  by 
spectro-colorimetric  methods  is  described  in  G.  and  H.  Krtiss* 
work  on  Colorimetry  and  Quantitative  Spectrum  Analysis. 


1  Liveing  and  Dewar,  P.  R.  S.  28,  367  ;  30,  93  ;  32,  189. 

8  P.  T.  (1864)  p.  139- 

»  N.  A.  S.  U.  (1868)  [3]  6.     Le  spectre  du  fer,  1884. 

4  Recherches  sur  le  spectre  solaire  (Upsala,  1868). 

6  P.  T.  (1873)  163,  270. 

6  Spectre  normal  du  soleil  (Paris,  1881). 

1  P.  R.  S.  (1894)  56,  192.  P.  T.  (1894)  185,  1029.  See  also  Lecoq  de 
Boisbaudran,  Spectres  lumineux  (Paris,  1874).  Liveing  and  Dewar,  P.  R. 
S.  (1879)  29,  402. 

8  Jour.  Chem.  Soc.  10,  79.     P.  M.  [4]  24,  417. 

9  7W</[4]24,  441. 

10  Ber.  11,  916.     Monatsber.  Berl.  Akad.  1878.  p.  412. 


SPECTRA    OF   THE  ELEMENTS. 


145 


Arc  and  spark 

spectra: 

6022.0 

6016.9 

6013.7 

542O.6* 

54I3-5* 

5377-7* 

53414* 

4823.7 

4783.6 

4765.9 

4762.3 

4754.2 

4739-2 

4730.0 

4727.6 

4710.0 

467i.6t 

4626.4! 

4607.4! 

4605.6! 

4548.9! 

4502.3 

4499.0 

4490.2 

4473-1 

4470.1 

4464.9 

4462.1 

4461.3 

4458.3 

4457-5 

4456.0 

4455-4 

(4455.1! 

4454.9!) 

4451.8 

4436.3 

4414.9 

4382.2! 

4375-  if 

4337-6! 

4325.9! 

4284.  5t 

4281.3 

4272.2! 

4266.3 

(4260.9 

4258) 

4235.4 

4227.6 

4083.8 

4080.3 

4055.0 

4048.9 

4041.3 

4033-2 

4030.9 

MANGANESE    OXIDE.1 


Spark-spectrum : 

6235  6205  b  6186   6179  b  5933 
55&o  5434   5424  b  5396   5392  b 


5848  b  5689   5684   5645  b  5608  b 
536ob  523ob  5193  b  5158  b 


MERCURY. 

'  The  earlier  observers  measured  the  spark-spectrum  under 
the  ordinary  pressure,  or  under  reduced  pressure  in  a  Geissler 
tube.  Liveing  and  Dewar2  were  unable  to  obtain  the  arc- 
spectrum,  but  Kayser  and  Runge 3  succeeded  in  doing  so 
without  difficulty. 

Arc  and  spark  spectra: 

6152.6^  5889.1*  5790.49  5769.45  5460.97  4916.41  4358.56 
4347.65  4078.05  4046.78  3663.25  3654.94  3650.31  3390.50 
3341.70  3131.94  3131.68  3125.78  2957.37  2925.51  2893.67 
2752.91  2655.29  2653.89  2652.20  2642.70  2576.31 
2534.89  2464.15  2446.96 


2759-83 
2536.72 


1  Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris,  1874).     Watts,  P.  M. 
[4]  45,  81.     Hartley,  P   T.  (1894)  185,   1029. 

2  P.  T.  (1883)  174,  218.- 

3  A.  B.  A.    1891.     See  also  Kirchhoff,  A.    B.  A.    1861.     Muggins,  P.  T. 
(1864)  p.    139.     Gladstone,    P.  M.    [4]   20,   249.      Plucker,    P.   A.    107,   497. 
Thalen,  N.  A.  S.  U.  (1868)  [3]  6.     Lecoq  de  Boisbaudran,  Spectres  lumineux 
(Paris,  1874).      Hartley  and  Adeney,  P.  T.  175,  136.      Pearce,  W.  A.  6,  597. 
H.  W.  Vogel,  Berl.  Monatsber,  1879,  P«  586.     Ederand  Valenta,  Denkschr. 
Wiener  Akad.  (1894)  61,  401. 


*  Visible  only  in  the  spark-spectrum.     (Thalen.) 
!  Visible  only  in  the  arc-spectrum.     (Thalen.) 


146  SPECTRUM  ANALYSIS, 


MOLYBDENUM. 

The  spectrum  of  this  element  has  not  been  thoroughly 
investigated.  Thalen,1  using  Leyden  jars,  examined  the  visi- 
ble portion  of  the  spark-spectrum;  Lockyer,8  in  addition, 
observed  about  35  arc  lines  between  \  =  4000  and  3900;  and 
W.  A.  Miller3  photographed  some  lines  in  the  ultra-violet, 
but  did  not  measure  them. 

Spark-spectrum : 

6030.2      5888.6      5857.6      5792.0      5751.2      5688.6     5570.2      5532.6 
5506.1      4278.3 

NICKEL. 

Thalen  *  used  nickel  electrodes  in  order  to  obtain  the 
spark-spectrum,  and  Lecoq  de  Boisbaudran 5  passed  sparks 
through  nickel  chloride  solutions;  like  Kirchhoff,8  they  only 
examined  the  visible  portion.  Angstrom's7  investigations  of 
the  arc-spectrum  were  limited  to  the  same  region.  Cornu,8 
I^ockyer,9  and,  more  recently,  Liveing  and  Dewar,10  have 
examined  portions  of  the  spectrum,  particularly  the  ultra- 
violet ;  and  Hasselberg11  has  recently  completed  a  careful  in- 
vestigation of  the  spectrum  between  D  and  A  =  345O.  The 
absorption-spectra  12  of  solutions  of  nickel  salts  are  not  very 

1  N.  A.  S.  U.    (1868)  [3]  6. 

2  P.  T.  173,  561.     P.  R.  S.  27,  280. 

3  P.  T.  (1862)  152,  861. 
4N.  A.  S.  U.  (1868)  [3]  6. 

6  Spectres  lumineux  (Paris,  1874). 
«  A.  B.  A.  1861. 

I  Recherches  sur  le  spectre  solaire  (Upsala,  1868). 

8  Spectre  normal  du  soleil  (Paris,  1881) 

9  P.  T.  163,  369:  173,  561. 

10  Ibid.  (1888)  179,  231. 

II  Svensk.  Vetensk.   Akad.  Handl.  (1896)  28,  No.  6.     Astrophys.  Jour. 
<i89<S)  3,  288  ;  4,  343  ;  (1897)  5,  38. 

12  H.  W.  Vogel,  Ber.  (1875)  8,  1537. 


SPECTRA    OF   THE  ELEMENTS. 

characteristic;  the  majority  produce  total  extinction  at  each 
end. 

Arc  and  spark  spectra: 


6177.0 

5893-13 

5761.10 

5754-86 

5715-31 

57I2.IO 

5709.80 

5695.22 

5682.44 

5664.28 

5649.90 

5625.56 

5615.00 

5594-00 

5592.44 

5588.12 

5578  98 

5510.28 

5477.13 

5436.10 

5371.64 

5168.83 

5155-92 

5146.64*    5142.96 

5137.23* 

5129.52 

5115.55* 

5100.13 

5099-50 

5084.27 

5082.55 

5081.30 

5080.70 

5049.01 

5042.35 

5035.55 

5017.75 

5000.48 

4984.30 

4980.36 

4918.53 

4904.56 

4866.42 

4855.57 

4831.30 

4829.18 

4786.66 

4756.70 

4714.59 

4703.96 

4686.39 

4648.82 

4606.37 

4605.15* 

4600.51 

4592.69 

4547.44 

4520.20 

4470.61 

4462.59* 

4459.21 

4437.17 

4410.  70 

4401.70 

4384.68 

4359-73 

4331.78 

4330.85 

4325.75 

4296.06 

4288.16 

4284.83 

4201.88 

4I95.7I 

4128.48 

3995-45 

3973.70*    3972.31 

3944  25 

3889.80 

3863.21 

3858.40 

3832.44 

3831.82 

3829.49 

3807.30* 

3793-75 

3792.48 

3783.67* 

3775.71 

3772.70 

3744.68 

3739.36 

3736.94 

3722.63 

3688.58 

3674.28 

3670.57 

3664.24 

3624.87 

3619.52 

3612.86 

3610.60* 

3609.44 

3602.41 

3597.84 

3588.08 

3571.99 

3566.50 

3551.66 

3548.34 

3528.13 

3524.65 

3919.90 

3515.17 

3514.06 

3510.47* 

3501.00 

3493.10 

3486.04 

3472.68 

3469.64 

3467.63 

3461.78 

3458.59 

3453-0 

3446.4 

3437-8 

3434.1 

3424-2 

3415.5 

34I5.I 

3414.6 

3408.3 

3394.1 

3392.1 

3381.7 

3375.0 

3370.6 

3362.6 

3321.9 

3317.3 

3244.5 

3236.0 

3234.4 

3197.4 

3179.6 

3134.0 

3101.99 

3101.67 

3087.0* 

3080.7 

3064.6 

3057  6* 

3054.3 

3050.8 

3037.9 

3019.2* 

3011.9 

3003.6 

3002.5 

2994-5 

2992.6 

2981.6 

2943.9 

2936.7* 

2928.8* 

2913.6 

2865.5+ 

2863.7* 

2821.2 

2805.4 

2684.4* 

2679.2* 

2647.2 

2639.9* 

2615.3* 

2610.0* 

2545-8 

2511.0 

2506.3* 

2484.0 

2473.2 

2454-1 

2441.9 

2437-9 

2421.2 

2416.4 

2413-2 

2394.7 

2394.4 

2393.0 

2382.2 

2375.4 

2356.3 

2345-1 

2341.1* 

2334.5 

2330.0 

2326.4 

2325.9 

2321.4 

2319.7 

2318.4* 

2316.0 

2314-0 

2312.2 

2311.0 

2303.7 

2302.9* 

2302.4* 

2296.6* 

2287.8 

2287.2 

2278.8 

2278.2 

2274-5 

2270.3 

2264.5 

2258.0 

2256.1 

2255.1 

2253.9 

2244.8 

2230.0 

2226.2 

2224.7 

2222.7 

222O.2 

2216.2 

2210.2 

2206.5 

2205.6 

2201.2 

2184.6 

2174-8 

2174.2 

NIOBIUM. 

Thalen 

unsuccessfully 

endeavored  to  measure 

the  lint 

which  are 

very  faint. 

Visible  only  in  the  spark-spectrum.       f  Visible  only  in  the  arc-spectrum. 


148  SPECTRUM  ANALYSIS. 


NITROGEN. 

In  addition  to  the  ordinary  spark  or  elementary  spectrum, 
two  band-spectra  are  known,  one  produced  at  the  cathode, 
the  other  at  the  anode,  when  a  feeble  discharge  is  passed 
through  the  gas  contained  in  a  Geissler  tube.  The  spectrum 
obtained  with  powerful  sparks  consists  of  numerous  lines 
which  are  bright,  but  not  quite  sharp;  they  have  been  meas- 
ured by  Huggins  and  Thalen,1  whilst  Hartley  and  Adeney* 
subsequently  examined  the  blue  and  violet  ones.  Plucker 
first  observed  the  band-spectrum  at  the  anode  in  1858;  it  was 
noticed  a  little  later  by  van  der  Willigen;3  Plucker  and 
Hittorf,4  and  Lecoq  de  Boisbaudran,  published  drawings  of  it; 
and  it  was  accurately  measured  by  Angstrom  and  Thalen,5 
and  more  recently  by  Hasselberg.6  Angstrom  and  Thalen 
believed  that  the  spectrum  was  not  due  to  nitrogen,  but  to  an 
oxygen  compound,  and  this  view  was  supported  by  Schuster/ 
who  observed  that  the  spectrum  disappears  if  the  gas  is  heated 
with  sodium,  which  he  thought  absorbed  the  oxygen;  but 
Salet 8  showed  that  the  spectrum  is  obtained  in  these  circum- 
stances if  the  metal  is  previously  saturated  with  nitrogen. 
Since  that  time  this  spectrum  has  been  universally  ascribed  to 
nitrogen;  it  consists  of  channelled  spaces  sharply  defined 
towards  the  red,  and  shading  off  towards  the  violet.  Hassel- 
berg and  Piazzi-Smyth,9  using  instruments  of  high  dispersive 

1  N.  A.  S.  U.  (1875)  [3]  9.     (From  5942-7  to  4641.0.) 

2  P.  T.  (1884)  175, .91.     (From  4629.7  to  3995.2.) 

3  P.  A.  106,  610. 
P.  T.  155,  i. 

N.  A.  S.  U.  (1875)  [3]  9. 

Mem.  de  1'Acad.  St.  Petersb.  (1885)  [7]  32,  No.  15. 

P.  R.  S.  20,  482. 

A.  c.  p.  [4]  28,  52.     C.  r.  82,  223,  274. 

P.  T.  E.  32,  416.  See  also  Angstrom,  P.  A.  94,  141.  Wiillner,  P.  A. 
135,  524;  137,  356  ;  147,  325  ;  149,  103.  H.  C.  Vogel,  P.  A.  146,  569. 
Deslandres,  C.  r.  103,  375.  A.  c.  p.  [6]  14,  257. 


SPECTRA    OF   THE  ELEMENTS.  149 

power,  succeeded  in  resolving  the  bands  into  groups  of  sepa- 
rate lines.  The  band-spectrum  at  the  cathode  was  differ- 
entiated from  that  at  the  anode  in  1858  by  Dove,1  and  van 
der  Willigen,2  but  subsequently  Pliicker  and  Hittorf  stated 
that  they  were  identical.  The  principal  bands  were  measured 
ten  years  later  by  Angstrom  and  Thalen.3  Hasselberg4  sub- 
sequently resolved  them  into  bright  sharp  lines,  which  are 
totally  different  from  those  at  the  cathode,  although  their 
appearance  is  similar.  Trowbridge  and  Richards6  state  that, 
with  a  powerful  continuous  discharge,  nitrogen  exhibits  its 
channelled  spectrum,  but  the  introduction  of  a  condenser 
causes  a  change  to  the  bright  line-spectrum.  In  connection 
with  nitrogen  the  spectra  of  some  of  its  compounds  and  of 
air  are  of  interest.  The  line-spectrum  of  air  is  composed  of 
the  spectra  of  nitrogen  and  oxygen;  it  is  always  observed 
when  sparks  are  passed  between  metal  electrodes  in  air,  and 
requires  particular  notice  in  order  to  avoid  errors  in  the  inves- 
tigation of  spark-spectra.  The  air  lines  usually  extend  equally 
sharply  over  the  whole  breadth  of  the  spectrum,  whilst  the 
metallic  lines  often  form  aggregates  proceeding  from  the  poles. 
An  absorption-spectrum  is  produced  by  considerable  thick- 
nesses of  air,  particularly  in  presence  of  water  vapor;  in  solar 
observations  this  causes  some  of  the  Fraunhofer  lines,  the 
intensity  of  which  differs  with  the  position  of  the  sun,  and 
depends  on  the  thickness  of  air  which  its  rays  traverse. 

Ammonia  exhibits  a  line-spectrum  when  burnt  in  air  in  a 
hydrogen  flame,  or  in  oxygen  in  an  oxyhydrogen  flame;  it  has 
been  measured  by  Dibbits,  Hofmann,  Lecoq  de  Boisbaudran, 
Magnanini,  and  Eder.  The  principal  band  extends  from  the 

1  P.  A.  104,  184. 

2  Ibid.  106,  626. 

»  N.  A.  S.  U.  (1875)  [3]  9- 

4  Mem.  de  1'Acad.  de  St.  Petersb.  (1885)  [7]  32,  No.  15.     See  also  H.  C. 
Vogel,  P.  A.  (1872)   146,  569.      Deslandres,  C.   r.  103,  375.     A.  c.  p.  (1888) 
[6]  14,  257. 

5  Amer.  Jour.  Sci.  (1897   [4]  3,  117.     P.  M.  43,  135. 


ISO  SPECTRUM  ANALYSIS. 

red  to  the  beginning  of  the  violet,  and  consists  of  numerous 
lines  or  bands,  some  sharp  and  some  aggregated,  but  showing 
no  regularity  in  structure.  A  second  band  is  composed  of 
sharp  lines;  the  remaining  five  bands  closely  resemble  each 
other  in  structure.  Their  sharp  edges  are  directed  towards 
the  red,  and  the  other  ends  may  be  resolved  into  numerous 
slender  lines  grouped  with  tolerable  regularity. 

Amines  when  burnt  in  oxygen  do  not  exhibit  character- 
istic spectra. 

Nitrous  Anhydride  (NO  +  NO2)  gives  an  absorption- 
spectrum  which  was  observed  by  Brewster  in  1832,  but  not 
described  until  1860;  his  drawing  cannot  be  reduced  to 
measurements,  as  no  scale  is  given.  The  spectrum  was 
accurately  examined  by  Hasselberg  in  1878  between  B  and 
A  =  4600;  it  is  extremely  complex,  partly  because  it  varies 
with  the  quantity  of  gas,  partly  from  the  large  number  of  lines 
and  bands,  which  are  not  arranged  according  to  any  definite 
plan. 

The  spectra  of  the  electric  discharge  in  liquid  nitrogen, 
air, and  oxygen  have  been  investigated  by  Liveing  and  Dewar;1 
they  consist  of  a  continuous  spectrum,  of  bright  lines  derived 
from  the  electrodes,  and  of  comparatively  feeble  bands 
apparently  emanating  from  the  molecules  of  the  liquid.  The 
continuous  spectrum  is  also  probably  due  to  the  electrodes. 
Briihl 2  has  determined  the  spectrometric  constants  of  nitro- 
gen, and  has  endeavored  to  elucidate  the  spectro-chemical 
relationship  of  its  compounds. 

Line-spectrum  of  nitrogen : 

5942.7  5933.1  5679.1  5675.6  5667.1  5542.2  5535.1 

5531.1  54Q6.I  5480.0  5045.9  5025.9  5016.9  5010.9 

5005.9  5002.9  4994.4  4988.0  4804.1  4789.1  4780.1 

4641.0  4629.7  4606.4  4600.9  4446.8  4348.8  (4237.0 

4229.5)  3995-2 

1  P.  M.  [5]  38,  235.     Ber.  (1895)  28,  4. 

2  Ztschr.  phys.  Chem.   16,  193,  225.     Ber.  26,  806,  2508;  28,  2388,  2393, 
2399- 


SPECTRA    OF   THE   ELEMENTS. 


Band-spectrum 
ment  of  the  bands: 


at  the  anode.      Lines  at  the  commence- 


6623.4 

6126.9 

5754.8 
5442.1 
5213.7 

4918.6* 
4270.0* 

6544.4 
6069.4 

5707.3 
5407.2 

5184.5 
4723.6* 

4201.6* 

6468.3 
6013.4 
5660.2 

5372.6 

5155.4 
4649.4* 
4141.7* 

6394.  2 

5958.9 
5614.9 

5339-5 
5126.9 

4574-3* 
4094.9 

6322.4 
5905.6 
5570.1 
5306.7 

5099.5 
4490.2* 

4059.3* 

6252.6 
5854.1 
5515.4 
5275.0 
5069.1* 
4416.6* 
3998.5* 

6185.5 
5803.9 

5478.4 
5244.1 
4976,6 
4357-5 

Band-spectrum 
ment  of  the  bands: 


at  the  cathode.      Lines  at  the  commence- 


5228.5 
4278.6 


4709.5 
4236.9 


4652.1 
4I99-3 


4600.2 
4167.0 

AIR. 


4554.6   4516.1    4485.7 


Spark-spectrum  i1 

6563.1  5942.6  5933  1  5679.1  5775-6  5667.1  5542.2  5535.1 

5531.1  5496.1  5480.0  5045.9  5025.9  5016.9  5011.0  5006.0 
5003.0  4994.5  4988.0  4804.1  4789.1  4780.1  4707.6  4699.1 
4648.0  4642.0  4629.7  4606.4  4600.9  4446.7  44i6.l2  4414.3- 
4348.8  43I9-3  4241-2  4237-0  4229.5  4075.8  4072.1  4069.9 

3995.2  3973-2  3955-5  3919-2  3749-6  3727-1  3438.1  3333-7 
3331-5  3309.2 

Absorption-spectrum.2     Telluric    Fraunhofer    lines.      See 
also  Rowland's  table  of  wave-lengths,  p.  191 : 

1  Thalen,   N.   A.   S.    U.   (1868)  [3]  6  (w.-l.  6563.1-4699.1).     Hartley  and 
Adeney,    P.  T.  (1884)   175,  91   (w.-l.  4648.0-3309.2).     Kirchhoff,   A.   B.  A. 
1861.     Huggins,  P.  T.  (1864)    154,  139.     Lecoq  de    Bolsbaudran,  Spectres 
lumineux  (Paris,   1874).      Plilcker  and   Hittorf,  P.  T.  (1865)   155,  i.     Gold- 
stein, W.  A.  (1882)  15,  280. 

2  Becker,  T.  R.  S.  E.  (1890)  36,  i.     Brewster,  P.  T.  E.  1833.     Brewster 
and  Gladstone,  P.  T.  (1860)  150.     Angstrom,    Recherches   sur   le  spectre 
solaire(Upsala,  1868).      Piazzi-Smyth,  Madeira  spectroscopic  (Edinb.  1882). 
Fievez,    Spectre   solaire   (Bruxelles,    1883).      Egoroff,    C.    r.  97,    555  ;   101, 
1143.     Hautefeuille  and  Chappuis,  C.  r.  93,  80.     Cornu,  A.  c.  p.  [6J  7,  i.  C. 
r.  95,  801.     Abney,  P.    R.    S.   (1885)   348.   C.    r.    97,  1206.     Hennesay,  P. 
R.  S.  (1870)  19.  P.  T.  (1875)  165.     Langley,  C.  r.  97,  555.    Janssen,  A.  c.  p. 
(1871)  [4]  23;  C.  r.  (1863)  56,  538;  (1865)  60,  213;  (1866)  63,  289;  (1874)  78, 
995  ;  (1885)  101,  in,  149;  (1886)  102  ;  (1888)  106;  (1888;  107;  (1889)  108. 
Secchi,  C.  r.  (1865)  60,  379.     Thollon,  Ann.  de  1'Obs.  de  Nice  (1890)  3. 


*  Triplets. 


152 


SPECTRUM  ANALYSIS. 


6020.33    5999.83 

5997- 

43 

5994 

-74     (5992.17 

5992. 

01) 

5991- 

03 

5990.74    5989-44 

(5988. 

75 

5988.67) 

5987-20 

5985. 

37 

5977.94 

5977 

.14      5976.94 

5975- 

27 

5971 

-53 

5970.24 

5969. 

24 

5968. 

49 

5967 

.87      5967.66 

5966. 

81 

(5966 

.42 

5966.33) 

5962. 

65 

5958. 

85 

(5958 

.48      5958.42) 

5958. 

02 

5955 

.10 

5951-68 

5950. 

49 

5949- 

92 

5949.42      5949-25 

5948. 

35 

5947 

-24 

5947-02 

5946.14 

5945- 

81 

5945 

.39      5944.84 

5944- 

42 

5942 

-73 

5942-57 

5941. 

73 

5941- 

19 

5935 

.96      5932.96 

5932. 

28 

(5928.53 

5928.43) 

5925. 

19 

5924. 

49 

5923 

.98      5923-82 

5922. 

66 

5920 

-73 

5919.85 

5919. 

22 

5918. 

62 

5913 

.15     (5910.95 

5910. 

87)     59io 

-25 

5909.14 

5902. 

25 

5901. 

68 

5900 

.22        5900.06 

5899- 

17 

5898 

-39 

5896.97 

5895. 

26 

5895. 

ii 

5893 

.72        5892.59 

5891. 

37 

5891 

-73 

5890.34 

5889. 

78 

5887. 

36 

5886 

.12        5884.04 

5859. 

73 

5745 

.92 

5742.30 

5737- 

82 

5727. 

18 

5722 

-07        5719.75 

5699- 

52 

5698.31 

5692.57 

5690.62 

5687, 

66 

5125 

.20        5068.88 

5067. 

29 

5060.  19 

5056.58 

5Ql8, 

55 

AMMONIA.1 

Flame-spectrum: 

Band     a 

6667—3572: 

6330 

6293 

6189       6051 

6006       5973 

5950 

5703 

5694 

(5271 

5263) 

Band     ft 

3433—3396: 

3370.8 

3360.3 

Band     y 

2719—    ?    : 

2719.2 

2718.1 

2710 

.9     2709.1 

Band     d 

2595—2500: 

2595.6 

2594-3 

2587.7     2586.2 

Band     e 

2479—2406: 

2478.* 

J 

2477.4 

2471 

5     2470.3 

Band     ? 

2371  —  2308: 

2370.* 

\ 

2370 

2364.5     2363.4 

Band     ij 

2272  —  2210: 

2272 

2271 

2265 

2263 

NITROUS   ANHYDRIDE.2 

(N02  +  NO.) 

Absorption-spectrum  : 

6165.7 

6127.3        6122.1 

5929.1 

5921 

•4        5790 

•  7 

5753 

•  5 

5730.4 

5654-0 

5645.6        5643.1 

5636.7 

5634-0        5531 

•  5 

5529 

.2 

5490 

•  7 

5463-3 

5452.1         5431-3 

5393-5 

5390-4        5385 

•3 

538o 

.2 

5340 

.2 

5264.6 

5260.2        5252.3 

5243.8 

5241 

•2           5230 

.6 

5225 

.1 

5220 

.0 

1  Magnanini,  Atti  della  R.  Accad.  dei  lincei  [4],  5,  900  (w.-l.  6667-4493). 
Eder,  Denkschr.  Wiener  Akad.  (1893)  60  (w  -1.  5080-2210).  Dibbits,  Die 
spectraal  Analyse,  1863.  P.  A.  (1864)  122,  497.  Schuster,  B.  A.  R.  1872. 
Mitscherlich,  P.  A.  (1863)  121,  459.  Lecoq  de  Boisbaudran,  C.  r.  101,  43. 
Hofmann,  P.  A.  (1872)  147,  92. 

4  Hasselberg,  Mem.  de  1'Acad.  St.  Petersb.  (1878)  [7]  26,  No.  4.  Brew- 
ster,  P.  T.  E.  12,519.  P.  A.  28,  385;  37,  50.  P.  T.  (1860)  150,  157. 
Morren,  P.  A.  141,  157.  Gernez,  C.  r.  74,  465.  Moser,  P.  A.  160,  177. 
Bell,  Am.  Chem.  J.  (1885)  7,  32. 


SPECTRA    OF   THE   ELEMENTS.  153 

5215.8  5208.0  5200.7  5196.0  5191.8  51248  5096.0  5046.5 
5032.8  5028.0  4966.6  4964.8  4947-2  4942.7  4903.9  4886.4 
4883.2  4813.0  4798.2  4793-8  4747.6  4680.6  4644.6 

OSMIUM. 

Thalen1  observed  only  a  single  line  in  the  spectrum  of  this 
element;  Huggins,3  in  the  visible  region,  noticed  seventeen 
others,  and  Lockyer 3  four  additional  ones  between  X  =  4000 
and  3900.  Rowland  and  Tatnall  *  have  recently  measured 
the  arc-spectrum  between  A  =  3000  and  4600;  the  lines  are  all 
comparatively  faint,  especially  the  double  one. 

Arc  and  spark  spectra: 
4422.7*      4420.633      4260.993      4135.945      (4097.090      4097.004)      4066.848 

OXYGEN. 

o 

The  spark-spectrum  of  air  was  first  measured  by  Ang- 
strom 5  (comp.  nitrogen),  who  did  not  distinguish  the  oxygen 
from  the  nitrogen  lines;  this  was  first  done  by  Huggins/ 
Pliicker  and  Hittorf7  examined  the  spectrum  of  oxygen 
enclosed  in  a  Geissler  tube,  but  failed  to  get  concordant 
results  in  consequence  of  the  presence  of  carbon  monoxide, 
which  is  so  readily  produced.  Schuster8  found  a  compound 
line-spectrum  at  the  anode,  and  a  band-spectrum  at  the 
cathode.  The  elementary  line-spectrum  is  obtained  by  pass- 
ing sparks  from  a  Leyden  jar  through  oxygen  under  the 
ordinary  pressure. 

The  absorption-spectrum  is  only  produced  by  a  consider- 
able thickness  of  the  gas;  it  is  the  origin  of  some  of  the 

N.  A.  S.  U.  (1868)  [3]  6. 

P.  T.  1864,  p.  139. 

Ibid.  (1881)  173,  561      See  also  Eraser,  C.  N.  8,  34. 

Astrophys.  Jour.  (1895)  2,  186. 

P.  A.  (1855)  94,  141. 

P.  T.  154,  146. 

Ibid.  155,  23.     Plucker,  P.  A.  (1859)  107,  518. 

P.  T.  (1879)  170,  37.     W.  A.  7,  670. 


*  Spark-spectrum. 


154  SPECTRUM  ANALYSIS. 

telluric  lines  in  the  solar  spectrum.  The  presence  of  oxygen 
in  the  sun.  is  still  an  open  question.  The  spectrum  of  the 
electric  discharge  in  liquid  oxygen  consists,  according  to 
Liveing  and  Dewar,1  of  a  few  obscure  absorption-bands. 
Bright  lines  produced  by  the  electrodes  are  also  visible, 
together  with  a  continuous  spectrum  which  is  ascribed  to 
solid  particles  detached  from  them. 
Elementary  line-spectrum: 

6171.7  (A.  &Th.)    5206.4  4816.6  4802.4  4782.6  4710.2  4705.4 

4694.1  4651.0  4649.2  4643-4  4641-9  4638.9  4630.7  4621.4 
4614,0  4607.2  4601.4  4596-2  4592.9      4592.0  4590.9  4583.1 
4544-5  4520.5  4507-7  4503-0  4447-1  4417-2  44I5-O  4366.9 
4353-7  4351-4  4349-3  4347-9  4345-5  4319-5  4317-2  4279-9 
4190.0  4185.3  4119.4  4109.8  4105.2  4105.0  4076.2  4072.3 

4070.2  3995-1  398i.4  3973-6  3956.2  3954-8  3919-3  3882.4 
3755-3  3749-8  (Tr.  &  H.)  3139-4  3135-3  (Desl.) 

Compound  line-spectrum.     At  the  anode: 

6157-9       5436.5       5330.4       4368. 2  (Sch.) 

3956.0       3948-9       3824.4       3692.4       2883.5  (Desl.) 

Band-spectrum.     At  the  cathode: 
b  (6010     5960)       b  (5900     5840)       b  (5630     5553)       b  (5292     5205) (Sch.) 

PALLADIUM. 

The  spark-spectrum  of  palladium  is  obtained  by  means  of 
powerful  discharges  from  a  Leyden  jar,  passed  between 
electrodes  of  the  metal,  or  through  a  solution  of  the  chloride. 

1  P.  M.  38,  235.  Ber.  (1895)  28,  4.  The  spectra  of  oxygen  have  also 
been  observed  by  the  following  :  Trowbridge  and  Hutchins,  P.  M. 
(1887)  [5]  24,  302.  Deslandres,  A.  c.  p.  (1888)  [6]  14,  257.  Wullner,  P.  A. 
130,  515;  137,  350;  144,  481;  147,  329.  W.  A.  8,  253.  Salet,  A.  c.  p.  [4] 
28,  52.  Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris,  1874).  Ang- 
strom and  Thalen,  N.  A.  S.  U.  (1875)  [3]  9.  Paalzow  and  H.  W.  Vogel,  W.  A. 
13,  336.  Piazzi  Smyth,  P.  T.  E.  (1882)  30,  419.  P.  M.  [5]  13,  130.  Janssen, 
C.  r.  118,  1007.  Hartley  and  Adeney,  P.  T.  (1884)  175,  91.  Neovius, 
Bihang  til  Svenska  Det.  Akad.  Handl.  17,  Afd.  i,  No.  8.  W.  A.  Beibl. 
(1893)17,563-  Eisig,  W.  A.  (1894)  51,  747.  Hasselberg,  W.  A.  (1894)  52, 
758.  Trowbridge,  P.  M.  (1896)  41,  450.  Runge  and  Paschen,  Astrophys. 
Jour.  (1896)  4,  317.  Lewis  E.  Jewell,  Ibid.  (1897)  5,  99. 


SPECTRA    OF   THE  ELEMENTS.  155 

Some  lines  in  the  ultra-violet  have  been  photographed  by 
Hartley,1  and  Rowland  and  Tatnall 2  have  measured  the  arc- 
spectrum  between  A  =  3000-4200.  The  lines  are  all  com- 
paratively faint. 

Arc  and  spark  spectra: 


5695.1 

5669.1 

5641.1 

5619.1 

5547-2 

5543-2 

5395.1 

5296.1 

5234.7 

5164.1 

5H7.4 

5110.9 

4875.5 

4818.1 

4788.1 

4474.4 

4213-1 

3958.772* 

3894.334* 

3690.483* 

3634.841* 

3609.696* 

3571.302* 

3553.236* 

3517.096* 

3489.915* 

3481.300* 

3460.884* 

3441.539* 

3433.578* 

3421.367* 

3404.725* 

3337-139* 

3302.256* 

3258.900* 

3251.760* 

3242.828* 

3114-152* 

PHOSPHORUS. 

The  line-spectrum  is  obtained  by  passing  sparks  through 
a  Geissler  tube  containing  phosphorus  vapor,  the  band-spec- 
trum by  the  introduction  of  phosphorus  vapor  into  a  hydrogen 
flame.  The  bands  are  most  clearly  visible  if  the  flame  is 
cooled  by  allowing  it  to  impinge  on  a  metal  plate  against  the 
other  side  of  which  a  stream  of  water  flows. 

Line-spectrum:3 

6506    6058    6033    5421    5403    5382    5338    5307 
5285    5244    4601    4589  (PI.  &  H.) 

Band-spectrum:4 

5995  br    5606  b    5264 br    5107  b  (L.  d.  B.) 

The  bands  marked  br  are  sharply  defined  towards  the  red 
and  shade  off  towards  the  violet. 

1  P.  T.  Dublin  (1882)  [2]  1. 

2  Astrophys.  Jour.  (1896)  3,  291.     See  also  Thalen,  N.  A.  S.  U.  (1868)  [3] 
6.     Kirchhoff,  A.   B.   A.    1861.     Huggins,    P.    T.  1864,   p.   139.     Lecoq   de 
Boisbaudran,  Spectres  lumineux  (Paris,  1874).     Lockyer,  P.  T.  (1881)  173, 
561. 

8  Pliicker  and  Hittorf,  P.  T.  (1865)  155,  24. 

4  Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris,  1874).  See  also 
Seguin,  C.  r.  (1861)  53,  1272.  Salet,  A.  c.  p.  (1873)  [4]  28,  56.  Christofle 
and  Beilstein,  C.  r.  (1863)  56,  399.  Mulder,  J.  pr.  Chem.  (1864)  91,  in. 
Lockyer,  P.  R.  S.  (1874)  22,  374.  Hofmann,  P.  A.  147,  92. 

*  Arc  spectrum. 


1 56  SPECTRUM  ANALYSIS. 


PLATINUM. 

The  spark-spectrum  is  obtained  by  the  use  of  powerful 
Leyden  jars  in  conjunction  with  platinum  electrodes,  or  a 
solution  of  platinum  chloride.  Gouy  l  obtained  the  spectrum 
by  mixing  platinous  chloride  with  the  gas  in  a  Bunsen  burner. 
The  measurements  of  Thalen/  Kirchhoff,3  Huggins,4  and 
Lecoq  de  Boisbaudran 5  are  confined  to  the  visible  region. 
Lockyer8  observed  twelve  lines  in  the  arc-spectrum  between 
A  =  4000-3900.  Rowland  and  Tatnall 7  have  recently  meas- 
ured the  arc-spectrum  between  A  =  3000-4600;  the  lines  are 
all  comparatively  faint,  especially  the  double  one. 

The  absorption-spectrum  of  platinum  chloride  solution 
consists  in  a  complete  extinction  of  the  blue  end  of  the  spec- 
trum; solution  of  potassium  platino-chloride  exhibits,  in 
addition,  a  rather  large  band,  the  middle  of  which  is  situated 
at  486^. 

Arc  and  spark  spectra: 

6523-3  5964-7  5479-0  5476-5  53QO.6         5368.6  5302.5 

5227.2  5060.4  4932.4  4899.0  4879-9  4852.9  4580.8 

4560.3  45528  4481.8  4455-0  4448.0        4445-7  4442.723* 
4440.7  4435-2  4430.4  4392«°  4291-1  (3283.436*  3283.332*) 
3064.824*  2998.079* 

POTASSIUM. 

The  compounds  of  this  element  are  readily  dissociated  by 
the  Bunsen  flame  and  exhibit  the  lines  of  the  metal;  the 
more  prominent  ones,  with  a  low  dispersion,  are  the  pair 

C.  r.  (1877)  85,  439. 
N.  A.  S.  U.  (1868)  [3]  6. 
A.  B.  A.  1861. 
P.  T.  1864,  p.  139. 
Spectres  lumineux  (Paris,  1874). 

P.  T.  (1881)  173,  561.     See  also  Hutchins  and  Holden,  P.  M.  (1887)  [5] 
24,  325.     Ciamician,  Wien.  Ber.  [2]  76,  499. 
n  Astrophys.  Jour.  (18951  2,  185. 

*  Arc-spectrum. 


SPECTRA    OF   THE   ELEMENTS.  I  57 

A  =  7699  and  A,  =  7665,  and  the  violet  one,  A.  =  4044. 
Lockyer '  believed  that  four  of  the  potassium  lines  are  visible 
in  the  solar  spectrum,  the  absence  of  the  others  being  due  to 
the  dissociation  of  potassium  at  the  temperature  of  the  sun, 
and  that  the  visible  lines  constituted  the  spectra  of  the  sub- 
stances into  which  potassium  was  resolved.  Kayser  and 
Runge's8  accurate  measurements  have  shown  that  potassium 
lines  are  absent  from  the  solar  spectrum,  so  that  Lockyer's 
hypothesis  is  baseless.  E.  Becquerel 8  described  the  lines  A  —. 
10980,  1 1020,  and  12330  in  the  infra-red. 
Arc  and  spark  spectra: 

(7699.3          7665.6)*        6938.8  6911.2          5832.23*      5812.54 

5802.01*        5782.67*        4047-36         4044-29*       344749        3446.49 
3217.76  3217-27  3102.37         3102.15         3034.94 

RHODIUM. 

Thalen  unsuccessfully  endeavored  to  measure  the  faint 
lines  in  the  spectrum  of  this  element,  but  Rowland  and 
Tatnall4  have  recently  photographed  the  violet  and  ultra- 
violet lines  of  the  arc-spectrum  between  A  =  3000  and  4500. 

Arc-spectrum: 

4374.981  4211.304  3959.009  3856.654  3701.056  3692.502  3658.135 
3597.294  3583.252  3528.177  3502.674  3462.184  3435-039  3396.960 

1  P.  R.  S.  (1878)  27,  279. 

2  A.  B.  A.  1890. 

3  C.  r.  96,  1218  ;  97   72.     See  also  Bunsen  and  Kirchhoff,  P.  A.  110,  167. 
Kirchhoff,  A.  B.  A.  1861.      Huggins,  P.  T.  1864,  p.  139.     Rutherfurd,  Silli- 
man's  Journ.  [2]  35,  407.     Wolf  and  Diacon,  C.  r.  55,  334.     Thalen,  N.  A. 
S.  U.  (1868)  [3]  6.     Salet,  A.  c.  p.  (1873)  [4]  28,  56.     Lecoq  de  Boisbaudran, 
Spectres  lumineux   (Paris,    1874).     Liveing   and   Dewar,    P.    R.  S.  28,  367, 
471  ;  29,  398.    P.  T.  (1883)  174,  215.    De  Gramont,  C.  r.  (1896)  122,  1411, 1443. 

4  Astrophys.  Jour.  (1896)  3,  286. 


*  Visible  also  in  the  flame-spectrum 


158  SPECTRUM  ANALYSIS. 

RUBIDIUM. 

This  element  was  discovered  in  1860  by  Bunsen  and 
Kirchhoff '  with  the  help  of  the  spectroscope.  The  salts  are 
readily  dissociated  in  the  Bunsen  flame,  and  the  chief  lines  of 
the  metal  are  clearly  visible;  the  more  prominent  are  the  two 
violet  lines  /V  =  4215  and  4202,  and  the  two  red  ones,  A  = 
7811  and  6298. 

Arc  and  spark  spectra : 

7950*          7811*          6298.7*       6206.7*       5724.41*     5648.18*     4215.72* 
4201.98*     3591.74        3587-23       3351.03        3348.86 

RUTHENIUM. 

The  arc-spectrum  of  this  element  has  been  measured  by 
Rowland  and  Tatnall3  between  the  wave-lengths  2975-4200, 
the  lines  are  all  comparatively  faint,  especially  the  double 
ones. 

Arc-spectrum : 
4200.062      4080.757      3799-489      3799-042      3728.173      3727-073t    3499.095 

3436.883     3428.460    (3264.790     3264.688)  (3254.834     3254.670) 

SAMARIUM. 

This  element  was  termed  by  its  discoverer,  Marignac,  Yfi. 
The  name  samarium  was  given  by  Lecoq  de  Boisbaudran,3 
who  subsequently,  in  common  with  Kruss  and  Nilson,  con- 
sidered that  it  was  a  mixture  (comp.  didymium). 

1  P.  A.  113,  337.     See  also  Kayser  and  Runge,  A.  B.  A.  1890.     Thalen, 
N.  A.  S.  U.  (1868)  [3]  6.     Kirchhoff,  A.  B.  A.  1861.     Lecoq  de  Boisbaudran, 
Spectres  lumineux  (Paris.    1874^     Bunsen,  P.  A.  155,   230,  366.     Liveing 
and  Dewar,  P.  R.  S.  28,  367,  471. 

2  Astrophys.  Jour.  (1896)  3,  288. 

3  C.  r.   89,  212,  516  ;  114,  578  ;  116.  6n,  674.     See  also  Thalen,  Ofver- 
sigt  K.  Vetensk.   Akad.  Forhandl.  (1881)  40,   No.   7.     Soret,  C.  r.   91,  378. 
Cleve  Ofversigt  K.  Vetensk.  Akad.  Forhandl.  (1881)  40,  No.  7. 

*  Visible  also  in  the  flame-spectrum. 
f  Also  Fe. 


SPECTRA    OF   THE  ELEMENTS. 


'59 


Spark-spectrum : 


5552.1 
5272.0 
4884.4 
4704.4 
4524.8 
4453-2 
4257-1 


5516.0 
5252.0 
4848.0 
4674.4 

4523.3 
4434.2 


5494-5 
5201.0 
4842.0 
4669.4 
4520.3 
4425.2 


5466.5 

5175.4 
4816.0 


5452.9 
5173.4 
4786.0 
4593-8 
4498.8 
439°- 7 


5368.5 
5117.8 

4783.5 
4581.8 

4478.3 
4347-6 


5341-4 
5053.3 
4760.5 
4567.8 
4467-2 
4319.1 


5320.9 
5044-8 
4746.0 
4544.8 
4458.2 
4297.1 


5283.0 

4911-4 

4728.9, 

4538.3 
4454-7 
4280.6 


SAMARIUM    NITRATE. 


Absorption-spectrum.1  Position  of  the  minimum  of 
brightness: 

5797      5759      5588      5282      5211      5005      4892     (4838      4750)     4634      4530 
4436      4175      4090 

SCANDIUM. 

The  discovery  of  this  element  was  made  by  Nilson. 
Thalen 2  measured  its  spark-spectrum,  which  consists  of 
numerous  lines;  solutions  of  its  salts  do  not  produce  absorp- 
tion-spectra. 

Spark-spectrum : 

6305.0  6247.0 
6072.6*    6065.1* 

5527.0  5520.5 

5240.0  5081.8 

4374.6  4325.1 


6239.0 

6210.9 

6154.1* 

6115.9* 

6101.5* 

6080.1* 

6038.0* 

5700.5 

5687.0 

5672.0 

5657.5 

5641.0 

55I4.5 

5484.9 

5481.9 

5392-3 

5356.0 

5349-4 

5031.3 

4744-0 

4740.4 

4670.4 

4415.7 

4400.7 

4320.6 

4314.6 

4249.1 

SELENIUM. 

The  line-spectrum  is  obtained  by  passing  sparks  from  a 
Leyden  jar  through  a  Geissler  tube  containing  selenium 
vapor;  with  a  feebler  current  a  band-spectrum  is  produced. 
Salet 3  states  that  the  former  is  also  obtained  by  passing  sparks 
between  platinum  electrodes  which  have  been  covered  with 

1  G.  Krliss  and  Nilson,  Ber.  20,  2144. 

0  Ofversigt  K.  Vetensk.  Akad.  Forhandl.  (1881)  38,  No.  6,  p.  13,    Journ. 
de  Phys.  [2]  35,  446. 

3  Spectroscopie  (Paris,  1888).     A.  c.  p.  (1873)  [4]  28,  47. 

*  Bands  shading  off  towards  the  red. 


l6o  SPECTRUM  ANALYSIS. 

melted  selenium,  whilst  he  observed  the  latter  in  a  coal-gas 
or  hydrogen  flame  in  which  selenium  was  burning.  Gernez  * 
has  examined  the  absorption  spectra  of  the  vapors  of  selenium, 
selenious  chloride,  selenious  bromide,  and  selenious  anhydride. 
Spark-spectrum  of  the  vapor: 

6055   5306   5272   5254   5226   5174   5142   5097   5093   4996 
4979  (4845   4841)  4764   4M   4604 

Band-spectrum: 

5871   5751   5621   5491   5371   5271   5i66   5031   4951   4851 


SILICON. 

The  earlier  observers  of  the  visible  portion  of  the  spark- 
spectrum' of  this  element  are  Pliicker,2  Kirchhoff,  and  Salet.* 
In  Rowland's4  table  of  wave-lengths  some  lines  in  the  arc- 
spectrum  are  given  which  are  not  mentioned  by  previous 
workers.  Concordant  measurements  in  the  ultra-violet  have 
been  made  by  Hartley  and  Adeney,5  and  Eder  and  Valenta6 
of  the  spark-spectrum,  and  by  Liveing  and  Dewar,7  and  Row- 
land of  the  arc-spectrum. 

Spark-spectrum : 


6366 

6341 

5981 

5960 

59-18.76 

5772.36 

5708.62 

5645-84 

5057 

5041 

(4131.5 

4126.5) 

4103.10 

3905.67 

2987.77 

2881.70 

2631.39 

2528.60 

2524.21 

2519.30 

2516.21 

2514.42 

2506.99 

2435.25 

2216.76 

1  C.  r.  (1872)   74,  803,  1190.     See  also   Mulder,  J.  pr.  Chem.  (1864)  91, 
113.     Pliicker  and    Hittorf,  P.    T.    (1865)    155,    5.     C.   r.    73,  622.     A.   de 
Gramont,  C.  r.  (1895)  120,  778. 

2  P.  A.  (1859)  107.  531- 

3  Spectroscopie  (Paris,  1888).     A.  c.  p.  (1873)  [4]  28,  65. 

4  Astronomy  and  Astrophysics  (1893)  12,  321. 

5  P.  R.  S.  35,  301. 

6  Denkschr.  d.  Wien.  Akad.  (1893)  60,  257. 

7  P.  T.  174,  222.     See  also  Troost  and  Hautefeuille,  C.  r.  (1871)  73,  920, 
Mitscherlich,  P.  A.  (1863)  121,  459.     Ciamician,  Wien.  Ber.  (1880)  82,  435, 


SPECTRA    OF   THE   ELEMENTS.  l6l 


SILVER. 

The  spark-spectrum  of  silver  has  been  measured,  in  the 
visible  portion,  by  Kirchhoff,1  Thalen,2  Huggins,3  and  Lecoq 
de  Boisbaudran,4  and  a  part  of  the  ultra-violet  by  Hartley 
and  Adeney.  Lockyer,5  and  Liveing  and  Dewar6  only 
observed  a  few  lines  in  the  arc-spectrum,  which  was  accurately 
measured  by  Kayser  and  Runge.7  They  obtained  the  spec- 
trum by  volatilizing  silver,  or  crystals  of  silver  nitrate,  in  the 
carbon  arc.  Silver  electrodes  could  not  be  used,  as  they  at 
once  melted,  probably  on  account  of  their  high  conductivity 
of  heat.  The  spectra  of  the  arc  and  spark  differ  considerably. 
The  brighter  lines  in  the  following  table  are  only  present  in 
the  latter;  but  Thalen,  Huggins,  and  Hartley  and  Adeney 
observed  a  number  of  fainter  lines,  which  are  also  absent  from 
the  arc-spectrum. 

Spark  and  arc  spectra: 

5623.5*      5471.72      5465.66      5209.25      4668.70      4476.29      4212.1        4055.44. 
3981.87      3383.00      3280.80      3130.09      2938.42      2824.50      2575.70      2375.1 
2312.5        2309.74 

SODIUM. 

Some  of  the  sodium  lines  are  obtained  with  extraordinary 
ease,  particularly  the  ZMines  and  the  less  refrangible  ultra- 
violet ones.  The  ZMines  with  a  low  dispersive  power  appear 
as  one,  and  the  particles  of  sodium  chloride  present  in  the  air 
are  sufficient  to  cause  their  production.  This  fact  has  exer- 
cised some  influence  on  the  development  of  spectrum  analysis, 

1  A.  B.  A.  1861. 

2  N.  A.  S.  U.  (1868)  [3]  6. 
8  P.  T.  1864,  p.  139. 

4  Spectres  lumineux  (Paris,  1874). 

5  P.  T.  (1874)  164,  805. 

6  Ibid.  (1884)  175,  109. 

7  A.  B.  A.  1892.     See  also  Mascart,  Ann.  de  1'  Ecole  normale  (1866)  4 


*  Visible  only  in  the  spark-spectrum.     (Thalen.) 


1 62  SPECTRUM  ANALYSIS. 

as  the  universal  occurrence  of  the  lines  could  not  be  ex- 
plained until  Swan,1  in  1856,  pointed  out  their  origin. 

The  reversal  of  the  sodium  lines  was  the  first  observation 
leading  to  the  formulation  of  KirchhorT's  law  of  exchanges, 
on  which  spectrum  analysis  may  be  said  to  be  based. 

Arc  and  spark  spectra:2 

8200.3  8188.3  6160.97  6154.43    [Z>i]  5896.16*  [Z>2]  5890.19* 

5688.43  5682.86  5I53-72  5I49-I9  4983-53  4979-30 

3303.07  3302.47  2852.91  2680.46 

STRONTIUM. 

Mitscherlich  obtained  the  line-spectrum  by  the  use  of  the 
oxyhydrogen  flame;  it  is  also  produced  by  the  passage  of 
sparks  through  a  solution  of  the  chloride,  but  the  best  effects 
are  given  by  the  volatilization  of  the  chloride  in  the  electric 
arc.  This  was  the  method  employed  by  Kayser  and  Runge.3 
In  the  Bunsen  flame  the  strontium  haloid  compounds  chiefly 
exhibit  their  individual  spectra,  together  with  the  band-spec- 
trum of  the  oxide,  and  the  blue  line,  A  =  4607.5,  of  the 
metal. 

1  T.  R.  s.  E.  (1857)  21. 

2  Kayser  and  Runge,  A.  B.  A.  1890.      Bunsen  and  Kirchhoff,  P.  A.  110 
167.     Kirchhoff,  A.    B.  A.   1861.      Attfield,   P.   T.    1862,  221.     Rutherfurd, 
Silliman's    Journ.    [2]    35,  407.      Huggins,    P.  T.    1864,    p.  139-     Wolf   and 
Diacon,  C.  r.  55,  334.     Miiller,  P.  A.  118,  641.     Thalen,  N.  A.  S.  U.'(i868> 
[3]  6.      Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris,  1874).     Lockyer 
P.  R.  S.  (1879)    29,    140.     Cornu,    Spectre    normal  du  soleil  (Paris,  1881). 
Bunsen,  P.  A.  155,  366.     Liveing  and  Dewar,  P.  R.  S.  28,  367,  471  ;  (1879) 
29,   398,  402.      E.  Becquerel,  C.  r.  94,   1218  ;  97,  72.      De  Gramont,  C.  r. 
(1896)  122,  1411,  1443- 

3  A.   B.   A.    1891.     See   also    Bunsen   and    Kirchhoff,    P.  A.    110,    167. 
Kirchhoff,  A.  B.  A.  1861.     Mailer,   P.  A.    118,  641.      Huggins,  P.  T.  1864, 
p.  139.     Mascart,  Annales  de  1'Ecole   normale  (1866)  4.     Thalen,  N.  A.  S. 
U.  (1868)  [3]  6.       Lockyer,  P.  T.  163,  639  ;  164,  311.       E.  Becquerel,  C.  r. 
96,  1218  ;  (1883^  97,  72.     Liveing  and  Dewar,  P.  T.  174,  217.     Rydberg,  W. 
A.  (1894)  52,  119. 


*  Visible  also  in  the  flame-spectrum. 


SPECTRA    OF   THE  ELEMENTS. 

Arc  and  spark  spectra: 


^550. 

53 

6408. 

65 

6386.74 

5543- 

49 

5540. 

28 

5535- 

01 

5522.02 

5504.48 

5486. 

37 

5481.15 

5451. 

08 

5257. 

12 

5238. 

76 

5229.52 

5225- 

35 

5222. 

43 

5156.37 

4968. 

ii 

4962. 

45 

4892.20 

4876.35 

4872.66 

4868. 

92 

4855-27 

4832. 

23 

4812. 

01 

4784. 

43 

4742.07 

4722. 

42 

4678. 

39 

4607.52* 

4531-54 

4438. 

22 

4361. 

87 

4338.oo 

43«5. 

6o 

4215. 

66 

4161.95 

4077 

.88 

4030. 

45 

3705. 

88 

3547.92 

4399-40 

3475-01 

3464-58 

3380.89 

3366. 

43 

3351. 

35 

3330.15 

3322. 

32 

3307. 

64 

3301.81 

2931. 

98 

STRONTIUM    CHLORIDE.1 

Flame-spectrum: 

6730    6599    6351 

STRONTIUM    OXIDE.3 

Flame-spectrum  : 

c,  ,t> 

686'3.5t        6747-2f        6628f        6499t        6465*        (6060        6/632)        4607.5 


SULPHUR. 

Sulphur  exhibits  both  a  line-  and  a  band-spectrum;  the 
former  was  first  observed  by  Seguin,3  who  passed  sparks 
through  a  mixture  of  hydrogen  and  sulphur  vapor;  Plucker 
and  Hittorf4  volatilized  sulphur  in  a  Geissler  tube,  and  em- 
ployed sparks  from  a  Leyden  jar.  This  general  method  is 
still  in  use;  it  suffers  from  the  disadvantage  that  powerful 
sparks  under  a  low  pressure  are  apt  to  decompose  any  sulphur 
compounds  in  the  glass,  and  so  give  rise  to  the  sulphur- 

1  Mitscherlich,  P.  A.  121,  459.      Lecoq   de    Boisbaudran,  Spectres  lumi- 
neux  (Paris,  1874).     Bunsen,  P.  A.  (1875)  155,  230. 

2  Lecoq  de   Boisbaudran,  Spectres  lumineux  (Paris,    1874).     Eder  and 
Valenta,  Denkschriften  Wiener  Akad.  (1893)  60,  473. 

3C.  r.  (1861)  53,  127. 
4  P.  T.  155,  13. 


*  Blue  line  visible  also  in  the  flame-spectrum. 

f  Bands  sharply  bordered  towards  the   red,   shading  off  towards    the 
violet. 

%  Middle  of  a  band. 


164  SPECTRUM  ANALYSIS. 

spectrum  when  it  is  not  desired.  The  band-spectrum  is 
obtained  by  the  passage  of  feeble  sparks  through  a  Geissler 
tube  containing  sulphur  vapor.  Salet 1  produced  it  by  vola- 
tilizing sulphur,  or  one  of  its  compounds,  in  a  hydrogen 
flame,  cooled  by  allowing  it  to  impinge  on  a  plate  of  metal  or 
marble,  on  to  the  other  side  of  which  a  stream  of  water  was 
directed.  This  spectrum  was  mapped  by  Salet,  and  by 
Plucker  and  Hittorf,  but  the  observations  are  limited  to  the 
visible  region,  and  are  too  inaccurate  to  show  more  than  the 
existence  of  the  bands.  The  flame  of  burning  sulphur 
exhibits  a  continuous  spectrum  which  extends  far  into  the 
violet. 

Line-spectrum: 

5660.7  5640.3  5604.9  5562.4  5508.3  547^-4  5451.9  5439.0  5430.7 

5342.6  5320.1  5215.4  5201.1  5143.3  5103.7  5033.3  5013.5  4994.7 

4926.0  4919.4  4902.8  4885.4  4816.6  4715.8  4552.3  4525.5  4485.9 
4464.7 

Band-spectrum. a     Bands   sharply   bordered   towards    the 
violet,  but  shading  off  towards  the  red  (Salet): 
5366    5221    5191    5089    5041    4991    4946    4841    4796    4656    4616    4471 

TANTALUM. 

The  lines  of  this  element  were  too  feeble  for  Thalen  to 
measure,  but  Lockyer3  observed  eighteen  of  them  in  the  arc- 
spectrum  between  A  =  4000  and  3900. 

TELLURIUM. 

The  line-spectrum  of  tellurium  *is  obtained  by  passing 
sparks  between  electrodes  of  the  element,  and  has  been  meas- 

1  A.  c.  p.  [4]  28,  37.     C.  r.  (1869)  68,  404.     See   also    Hasselberg,  Bull. 
Acad.  imp.  St.  Petersb.  (1880)  11,  307.    Astronomy  and  Astrophysics  (1893), 
12,  347.     Mulder,  J.  pr.  Chem.  (1864)91,  112.     Ditte,  C.  r.  73,  559.     Lock- 
yer, P.  R.  S.  22,  374.     Gernez,  C.  r.  (1872)  74,  803.     Angstrom,  P.  A.  137, 
300.     C.  r.  73,  368.     Ciamician,  Wien.  Ber.  77,  839  ;  82,  425.     Schuster,  B. 
A.  R.  1880,  p.  272.     Ames,  Astronomy  and    Astrophysics  (1893),   12.     De 
Gramont,  C.  r.  (1896)  122,  1326. 

2  Salet,  A.  c.  p.  [4]  28,  37.     C.  r.  (1874)  79,  1231. 

3  P.  T.  173,  561. 


SPECTRA    OF   THE  ELEMENTS. 


I65 


ured  by  Huggins,1  and  Thalen8  in  the  visible  region,  and  by 
Hartley  and  Adeney  3  in  the  ultra-violet.  Salet 4  produced  a 
band-spectrum  by  passing  a  discharge  through  a  Geissler  tube 
of  hard  glass  containing  tellurium;  to  facilitate  heating,  the 
tube  was  covered  with  metal.  The  spectrum  consists  of 
bands  in  the  red,  and  channelled  spaces  in  the  green  and 
blue;  they  are  sharply  bordered  towards  the  violet,  and  shade 
off  towards  the  red.  The  same  spectrum  is  produced  by 
volatilizing  tellurium  in  a  hydrogen  flame.  Gernez  5  investi- 
gated the  absorption-spectra  of  tellurium  chloride  and  bro- 
mide; they  consist  of  channelled  spaces,  the  former  in  the 
green  and  orange,  the  latter  chiefly  in  the  red  and  yellow. 
Spark-spectrum : 


6438.2 

'6047.2 

6013.7 

5974.1 

5936.2 

5782.0 

5756.1 

5707.6 

5648.  1 

5575-1 

5489.1 

5478.5 

5448.5 

5367.1 

53II-0 

5218.2 

5I53-I 

5104.9 

4302.1 

4275.0 

4260.4 

4221.7 

4062.0 

4054.8 

4006.7 

3984.5 

3969-3 

3948.7 

3841.9 

3736.1 

3726.7 

(3650.0 

3645-1) 

3617.8 

3552-4 

3520.9 

3496.9 

3456.7 

344L9 

3409-2 

3384.1 

3364-I 

3354-6 

3331-2 

3309.3 

(32820 

3275.3) 

3258.2 

3248.7 

3107.9 

3073-1 

3046.4 

3017.0 

2966.5 

2941.2 

(2894.7 

2893.7) 

(2868.1 

2860.4 

2857.4) 

(2845-3 

2840.4 

2823.6) 

2792-3 

(2769.0 

2766.9) 

2710.6 

(2697.0 

2694.5) 

2635.1 

2544.1 

2529.8 

2505.6 

2499.0 

2473-6 

(2448.2 

2438.4) 

(2413-7 

2411.8) 

(2404.1 

2400.4) 

(23867 

2384.2) 

2370.7 

2359.0 

(2332.4 

2325-9) 

2321.4 

2318.2 

2295.4 

(2281.0 

2277.6) 

(2266.6 

2261.0 

2257.0) 

2250.4 

{2248.4 

2247.7) 

2243.7 

2219.7 

(2211.6 

2209.9) 

(2192.6 

2190.1) 

2179.6 

THALLIUM. 

Thallium  salts,  heated  in  the  Bunsen  flame,  exhibit  the 
characteristic  green  line  of  wave-length  5350.65.  The  visible 
portion  of  the  spark-spectrum  has  been  investigated  by 


1  P.  T.  1864,  p.  139. 

*  N.  A.  S.  U.  (1868)  [3]  6  (w.-l.  6438.2-5104.9). 

3  P.  T.  (1883)  175,  63  (w.-l.  4302.1-2179.6). 

4  A.  c.  p.  [4]  28,  49.     C.  r.  73,  742.     Spectroscopie  (Paris,  i 

5  C.  r.  74,  1190.     See  also  Ditte,  Ibid.  (1872)  73,  622. 


1 66  SPECTRUM  ANALYSIS. 

Huggins,1  and  Thalen,2  the  ultra-violet  region  by  Hartley  and 
Adeney,8  and  Cornu.4  The  arc-spectrum  has  been  measured 
by  Liveing  and  Dewar,&  and  more  recently  by  Kayser  and 
Runge,6  who  usually  obtained  it  from  the  metal,  but  occa- 
sionally used  the  chloride;  they  photographed  it  between  the 
limits  63Oywju  and  2io/f/w.  The  numerous  lines  in  the  spark- 
spectrum  between  650;^  and  300;^  are  almost  all  absent 
from  the  arc-spectrum.  With  the  exception  of  the  green  line 
at  535/^,  and  a  faint  line  at  553W,  the  rays  of  thallium, 
which  are  powerful,  consist  wholly  of  ultra-violet  light. 
Arc  and  spark  spectra:  ' 

5948.7*  5350.65f  5153-6*  5079-4*  5053.9*  4982.5*  4736.5*  4110.2* 

3933.4*  3775.87  3529.58  3519.39  3229.88  2921.63  2918.43  2826.27 

2767.97  2709.33  2665.67  2609.08  2580.23  2552.62  2379.66  2316.01 
2237.91 

THORIUM. 

The  spark-spectrum  of  thorium  has  been  measured  by 
Thalen;7  Rowland8  records,  in  his  table  of  wave-lengths, 
several  additional  bright  lines  which  he  obtained  with  the  arc. 

Spark-spectrum: 


5538 
4382 

.o 
.2 

5446.9 
4281.6 

5375- 
4278 

5 
.1 

5350.67t 

4273-1 

4919. 
3575. 

9 

4864. 
3529. 

5 

55J 

4393. 
3519 

2 
34* 

1  P.  T.  (1864)  154,  139. 

2  N.  A.  S.  U.  (1868)  [3]  6. 

3  P.  T.  (1884)  175,  104. 
4C.  r.  (1885^  100,  1181. 

6  P.  R.  S.  27,  132.     P.  T.  (1883)  174,  219. 

6  A.  B.  A.  1892.     See  also  W.  A.  Miller,  P.  T.  (1862)  152,  861.     Lecoq  de 
Boisbaudran,  Spectres   lumineux  (Paris,  1874).     Crookes,   P.   T.  153,  277. 
P.  M.    [4]    26,   55.     Bunsen,    P.    A.    (1875)    155,    230,    366.     Lockyer   and 
Roberts,  P.  R.  S.  23,  344.     Ciamician,  Wien.  Ber.  76,  499. 

7  N.  A.  S.  U.  (1868)  [3]  6. 

8  Astronomy  and  Astrophysics  (1893)  12,  321. 


*  Visible  only  in  the  spark-spectrum.     (Thalen,  Hartley  and  Adeney.) 
f  Visible  also  in  the  flame-spectrum. 
\  In  the  arc-spectrum.     (Rowland.) 


SPECTRA    OF   THE  ELEMENTS.  l6/ 

THULIUM. 

This  element  was  discovered  by  Cleve  in  1879,  an^  its 
spark-spectrum  measured  by  Thalen.1  The  oxide  is  hardly 
perceptibly  volatile  in  the  Bunsen  flame,  but  exhibits  a  dis- 
continuous spectrum  consisting  of  the  bands  A  =  6840  and 
4760;  the  former  corresponds  with  the  absorption-bands 
shown  by  thulium  salts,  and  Thalen  describes  an  additional 
one  at  A  =  4650.  Kruss  and  Nilson  consider  that  thulium, 
like  other  -metals  of  the  rare  earths,  is  not  an  element  (comp. 
didymium). 

Spark-spectrum : 

5962.5    5897.0    5676.0    5306.6    5034.3   4733-9   4615-8   4522.8 
4481.8    4387-2    4360.1    4242.1    4204.6   4188.4   4107.3   4093.7 

TIN. 

The  spark-spectrum  is  obtained  by  the  use  of  tin  elec- 
trodes, or  of  a  concentrated  solution  of  a  salt;  it  has  been 
measured  by  Kirchhoff,2  Huggins,3  Thalen,4  and  Hartley  and 
Adeney;5  the  arc-spectrum  by  Liveing  and  Dewar,8  and 
Kayser  and  Runge.7  The  spectra  differ  considerably  in  the 
visible  region,  the  latter  only  contains  two  lines,  but  four 
additional  ones  are  included  in  the  spark-spectrum,  which  also 
contains  more  lines  in  the  ultra-violet.  Salet "  observed  a 
band-spectrum  of  the  oxide,  and  also  a  characteristic  reddish 
yellow  band  at  6io/f/w,  when  the  chloride  is  volatilized  in  a 
hydrogen  flame;  these  results  were  confirmed  by  H.  W. 
Vogel.' 

Ofversigt  K.  Vetensk.  Forhandl.  (1881)  40. 

A.  B.  A.  (1861). 

P.  T.  (1864)  154,  139. 

N.  A.  S.  U.  (1868)  [3]  6. 

Ibid.  (1884)  175,  104. 

P.  T.  (1883)  174,  219. 

A.  B.  A.  1893. 

A.  c.  p.  (1873)  [4l  28,  68. 

9  Prakt.  Spectralanalyse  (Berlin,  1889).  See  also  Mascart,  Ann.  de 
I'Ecole  normale  (1866)  4.  Lecoq  de  Boisbaudran,  Spectres  lumineux  (Paris, 
$874).  Lockyer  and  Roberts,  P.  R.  S.  (1875)  23,  344. 


1 68 


SPECTRUM  ANALYSIS. 


Spark  and  arc  spectra: 

6453.3* 

5799.0* 

5631-91 

5589.5* 

5563.5* 

4524.92 

3801.16 

3745-  7t 

3595.9:}: 

3352.3f 

3330.71 

3283.41 

3262.44 

3175.12 

3034.21 

3009.24 

2913.67 

2863.41 

2850.72 

2840.06 

2788.09 

2779.92 

2706.61 

2661.35 

2658.3f 

2643.6f 

2631.9f 

2594-49 

2571.67 

2558.12 

2546.63 

253L35 

•2495.80 

2483.50 

2429.58 

2421.78 

2408.27 

2354.94 

2334-89 

2317.32 

•2286.79 

2269.03 

2267.30 

2251.29 

2246.15 

2231.80 

2209.78 

2199.46 

2194.63 

2171.5 

2151.2 

2148.7 

2141.1 

2121.5 

2113.9 

2100.9 

2096.4 

2091.7 

2080.2 

2073.0 

2068.7 

2063.8 

2058.3 

2053.8 

TITANIUM. 

The  arc  and  spark  spectra  of  titanium  are  very  rich  in  lines 
which,  in  the  visible  region,  were  measured  long  ago  by 
Thalen,1  Angstrom,  Cornu,2  and  Liveing  and  Dewar.3  Lock- 
yer4  records  twenty-four  additional  lines  between  A,  =  4000 
and  3900,  and  Cornu  twenty-five  between  A  =  3510  and 
3217.  Hasselberg  5  has  recently  subjected  the  arc-spectrum, 
between  D  and  A,  =  3450,  to  a  thorough  investigation.  For 
its  production  he  introduced  a  fragment  of  rutile  into  the 
hollow  of  the  carbon  anode.  Rowland  has  identified  many 
of  the  solar  lines  with  those  of  titanium  ;  they  are  not  all 
given  in  the  list  below,  but  are  included  in  his  table  of 
normal  lines  in  Chapter  IX. 

Arc-spectrum  : 

6261.3  6258.6  6222.  o§  6215.  2§  6i26.3§  6098.  6§  6091.  6§  6084.4^ 

6065.  Sg  5999-8§  5979.  1§  5966.  5§  5953.  0§  5922.7  5920.0  5899.56 

5866.69  5804.45  5786.21  5774-27  5766.56  5762.52  5739-69  5715.30 
5714.12  5702.92  5689.70  5680.15  5675-61  5662.37  5648.81  5644-37 

5565.70  (5514.78   5514.58)  5512.72 

1  N.  A.  S.  U.  (1868)  [3]  6. 

2  Spectre  normal  (Paris,  1881).     Journ.  de  1'Ecole  polyt.  (1883)  52. 

3  P.  R.  S.  (1881^  32,  402. 

4  P.  T.  (1881)  173,  561. 

5  Svensk.  Vetensk.  Akad.  Hand.  (1895)  28,  No.  i.     Astrophys.  J.  (1896) 
3,  116;  4,  212. 


*  Visible  only  in  the  spark-spectrum.     (Thalen.) 

\  Visible  only  in  the  spark-spectrum.     (Hartley  and  Adeney.) 

\  3=98.9  cor.     (Watts.) 

§  Visible  in  the  spark-spectrum. 


1"  OF  THB  r 

UNIVERSITY 


SPECTRA    OF   THE  ELEMENTS. 


169 


5504.10 

5490.38 

5488.44 

(5482.09 

5481.64) 

5429-37 

5409-81 

5369.81 

5297.42 

5295.95 

5283.63 

5266.20 

5256.01 

5252.26 

5238.77 

5226.70 

5225.15 

(5224.74 

5224.46 

5223.80) 

5219.88 

5210.55 

5193.15 

5188.87 

5I73.94 

5152.36 

5M7.63 

5145.62 

5120.60 

5"3.64 

5087.24 

5064.82 

5040.12 

5038.55 

(5036.65 

5036.10) 

5025.72 

5025.00 

5023.02 

5020.17 

5016.32 

5014.49 

5013-45 

5007.42 

4999.67 

4997.26 

4991.24 

4989.33 

4981.92 

4975-52 

4928.50 

4921.90 

4919.99 

4913.76 

4900.08 

4885.25 

4870.28 

4868.44 

4856.18 

4841.00 

4820.56 

4799-95 

4792.65 

4778.44 

4759-44 

4758.30 

4742.94 

473L33 

4723.32 

4722.77 

4710.34 

4698.94 

4693.83 

4691-50 

4682.08 

4675.27 

4667.76 

4656.60 

4650.16 

4645-36 

4640.  1  1 

(4639-83 

4639.50) 

4629.47 

4623.24 

4617.41 

4572  -15 

4563-94 

4555.64 

4552.62 

4549-79 

4548.93 

4544.83 

4536.25 

4536.12 

4535-75 

4534-97 

4534-15 

4533-42 

4527.48 

4522.97 

4518.18 

4512.88 

4501.43 

4489-24 

4481.41 

4475.00 

4471.40 

4468.65 

4465.96 

4457-59 

4455-48 

4453-87 

4453.48 

4451.07 

4449-32 

4443-97 

4440.49 

4434-  i  5 

4430-55 

4427.28 

4426.24 

4423.00 

4417.88 

4417.46 

4404.42 

4399-92 

4395-17 

4394-04 

4369-82 

4338.05 

4326.50 

4325.30 

4321.82 

4318.83 

4314.95 

4314.50 

4313.01 

4306.07 

4302.08 

4301.23 

4300.73 

4300.19 

4299.79 

4299.38 

4298.82 

4295.91 

4294.28 

4291.07 

4290-37 

4289.23 

4287.55 

4286.15 

4285.15 

4282.85 

4281.49 

4274.73 

4263.28 

4256.18 

4238.00 

4186  27 

4171.15 

4163.80 

4I59.79 

4151.11 

4137.39 

4127.67 

4123.68 

4112.86 

4082.57 

4078.61 

4060.42 

4055.18 

4030.60 

4026.64 

4024.71 

4021.98 

4013.72 

4009.06 

3998.77 

3989.92 

3982.62 

3981.91 

3964.40 

3962.98 

3958.33 

3956.45 

3948.80 

3947.90 

3930.02 

3926.48 

3924.67 

39J4.45 

39I3-58 

3304.95 

3901.13 

3900.68 

3895-42 

3883.02 

3882.49 

3882.28 

3875.44 

3873-40 

3869.47 

3868.56 

3866.60 

3862.98 

3858.26 

3853.87 

3853.18 

3822.16 

3786.20 

3771.80 

3761.46 

3759.42 

3753.75 

3753-00 

374LI9 

3729.92 

3725.28 

3724.70 

3722.70 

3694-58 

3690,04 

3685.30 

3671.82 

3669.08 

3662.37 

3660.75 

3659-91 

3658.22 

3654.72 

3653.61 

3646.32 

3642.82 

3641.48 

3635.61 

3610.29 

3599-25 

3598.87 

3596.17 

3547-15 

3535.56 

3530.53 

3510.98 

3505-02 

349I-20 

3477-33 

TUNGSTEN. 


The  spectrum  of  this  element  is  obtained  by  means  of 
sparks  from  a  Leyden  jar,  and,  in  the  visible  region,  has 
been  measured  by  Thalen.1  In  the  arc-spectrum  Lockyer2 
observed  seven  additional  lines  between  A,  =  4000  and  3900. 


N.  A.  S.  U.  (1868)  [3]  6. 


2  P.  T.  (1881)  173,  561. 


I7O  SPECTRUM  ANALYSIS. 

Spark-spectrum: 

5734.1  5514.1  5492.6  5224.2  5071.4  5068.9  5053.9 
5014.9  5007.9  4888.5  4843.1  4302.6  4295.6  4269.6 

URANIUM. 

Thalen1  measured  the  lines  produced  by  the  passage  of 
powerful  sparks  from  a  Leyden  jar  through  a  solution  of  the 
chloride,  and  Lockyer2  observed  fifty-six  lines  in  the  arc- 
spectrum  between  A  —  4000  and  3900.  The  uranium  salts 
exhibit  characteristic  absorption-spectra,  which  have  been 
investigated  by  H.  W.  Vogel,3  Morton  and  Bolton,4  and 
Zimmennann;5  some  of  them  are  shown  in  the  following 
chapter.  The  spectra  of  the  uranic  and  uranous  salts  differ; 
the  latter  consists  of  a  strong  double  band  in  the  orange,  a 
feebler  band  in  the  green,  and  a  broader  one  in  the  blue; 
these  are  shown  when  a  uranic  salt  is  reduced  by  means  of 
zinc  and  hydrochloric  acid,  and  are  not  affected  by  the  pres- 
ence of  iron,  chromium,  cobalt,  nickel,  zinc,  or  aluminium 
(Vogel). 

Spark-spectrum : 

5914.1  5620.1  5580.2  5563-7  5523.1  55io.i  5494.6 
5482.5  5480.5  5478.0  5475.5  5385.1  5027.9  4732.0 
4724.0  4543-9  4473.4  4394-3  4374-7  4362.7  4341.2 

VANADIUM. 

Thalen6  has  measured  the  spark-spectrum,  and  Lockyer 
has  mapped  fifty  lines  in  the  arc-spectrum  between  A.  = 
4000  and  3900,  whilst  the  region  between  \  =  4450  and 

1  N.  A.  S.  U.  (1868)  [3]  6. 

2  P.  R.  S.  27,  280.     P.  T.  (1881)  173,  561. 

3  Prakt.  Spectralanalyse  (Berlin,  1889). 

4  C.  N.  (1873)  28,  47,    113,  164,  233,  244,  257,  268. 

5  Zeitschr.    Anal.    Chem.    23,    221.     See    also    Oeffinger,    Inaug.-Diss. 
Tubingen,  1866.     Stokes,  P.  A.  Suppl.-Bd.  (1854)  4,  273.     Hagenbach,   P. 
A.  (1872)  146,  395. 

6  N.  A.  S.  U.  (1868)  [3]  6. 

1  P.  R.  S.  27,  280.     P.  T.  (1881)  173,  561. 


SPECTRA    OF   THE  ELEMENTS. 


171 


4030  has  been  examined  by  Hasselberg1  in  his  investigation 
of  the  occurrence  of  vanadium  in  rutile. 


Arc 

and  spark  spectra: 

6241.7 

6120.1 

6090.2 

6040.2 

5726.1 

5703.6 

5698.6 

5669.1 

5627.1 

5623.6 

5415.4 

5241.1 

5234.2 

4881.9 

4875.5 

4844.  i 

4594.30 

4586.55 

4580.59 

4577o6 

4545.81 

4469-87 

4462.53  ' 

4460.39 

4459.92 

4452.17 

4444.40 

4441.90 

4438.01 

4416.65 

4408.65 

4408.40 

4407.90 

4406.85 

4400.75 

4  395-  40 

4390.15 

4384.90 

4379-42 

4353.05 

434LI5 

4333-  co 

4330.15 

4271.80 

4268.85 

4134.60 

4128.25 

4123.65 

4116.65 

4H5.65 

4115-30 

4112.00 

4109.95 

4105.30 

4100.00 

4095.60 

4092.87 

4090.  70 

YTTERBIUM. 

The  spark-spectrum  of  the  ytterbia  earths  has  been  meas- 
ured by  Thalen;2  no  absorption-spectrum  of  the  salts  is 
known. 

Spark-spectrum; 

6221.9         6005.0         5984.4         5837.0         5819.0        5556.6        &476.9 
5353.0         5347-4         5345-9         5335.0        4936.0        4786.5         4725.9 

YTTRIUM. 

The  spectrum  measured  by  Thalen  3  was  obtained  by 
passing  powerful  sparks  through  a  solution  of  the  chloride. 
Lockyer4  observed  twenty-six  lines  in  the  arc-spectrum 
between  A.  =  4000  and  3900.  Rowland  5  considers  it  pos- 
sible that  yttrium  is  composed  of  two  substances,  he 
includes  the  following  ultra-violet  lines  in  his  table  of  wave- 
lengths; they  were  observed  by  means  of  the  arc:  3950.50, 
3774.48,  3710,44,  3633-28,  3611.20,  3602.06,  3600.88, 
3584.66,  3549.15.  Crookes  '  has  described  a  phosphorescent 
spectrum  of  yttria. 

1  Bishang  till  Svenska.  Vetensk.  Akad.  Handl.  (1897)  22  Afd.  I.  No.7  ; 
23.  Afd.  I.  No.  3.  Astrophys.  Jour.  (1897)  5,  194  ;  6,  22. 

8  Ofvers.  K.  Vetensk.  Akad.  Forhandl.  1881. 

*  Om  spectra  Yttrium,  Erbium,  Didym  Och  Lanthan,  (Stockholm,  1874), 

4  P.  T.  (1881)  173,  561. 

8  Astronomy  and  Astrophysics  (1893),  12,  321.  Johns  Hopkins  Univ. 
Circulars  (1894),  13,  73.  See  also  Bunsen,  P.  A.  155,  366. 

6  P.  T.  174,  891.     A.  c.  p.  [6]  3,  145.     P.  R.  S.  35,  262:  38,  414. 


172  SPECTRUM  ANALYSIS. 

Phosphorescent  spectrum  of  yttria: 

Bands:   6676.7   6180.7   5737.9  5492-4   540O-5   4825.7   4323-6 

Spark-spectrum : 

6614.0      6435.5       6191.4      6181.9  6164.5       6150.1       6131.9      6019.5 

6009.5       6003.5       5987.4       5663.0  5605.6       5577-1       5545-6       5544-1 

5527.5       5521.0       5510.0       5497.0  5480.4       54739       5466.9       5403.0 

5206.0      5200.5       5123.3       5118.8  5088.3       4881.9      4855.0      4643.8 

4527.3      4422.7      4374.6      4309.6  4177.1       4167.7 


ZINC. 

The  spectrum  of  zinc  has  been  measured  by  Kirchhoff,1 
Huggins,2  Thalen,3  Lecoq  de  Boisbaudran,  Mascart,4  Cornu,6 
Lockyer,6  Liveing  and  Dewar,7  Hartley  and  Adeney,8  Ames,9 
and  Kayser  and  Runge.10  The  last  observers  volatilized  the 
metal  or  chloride  in  the  carbon  arc.  The  spark-spectrum 
differs  considerably  from  that  of  the  arc,  probably  on  account 
of  the  higher  temperature  of  the  former. 

Spark  and  arc  spectra: 

6363.7*      6103.0*      4924.6*      4912.0        4812.2        4810.71      4722.26 


4680.38      4630-06       3345-62       3345.13      3303.03       3302.67 
3075.99       3072.19      3035.93      3018.50       2801.00       2771.05 
2756-53       2712.60       2684.29       2670.67       2608.65       2582.57 
2567.99       2558.03       2542.53       2516.00       2491.67       2246.90 
2099-  if       2073.7!       2061.3!       2024.6! 

3282.42 
2770.94 
2570.00 
2138.3$ 

1  A.  B.  A.  1861. 
2  P.  T.  (1866)  154,  139. 
3  N.  A.  S.  U.  (1868)  [3]  6. 
4  Ann.  de  1'Ecole  normale  (1866),  4. 
6  J.  de  phys.  (1881)  10,  425.     C.  r.  (1885)  100,  1181. 
«  P.  T.  (1873)  163,  253,  639. 
1  P.  R.  S.  29,  402.     P.  T.  (1883)  174,  205. 
8  P.  T.  175,  63. 
•  P.  M.  (1890  V[5]  30,  33- 
10  A.  B.  A.  1891. 

*  Only  in  the  spark-spectrum  (Thalen). 
f  Only  in  the  spark-spectrum  (Corun). 
\  Only  in  the  spark-spectrum  (Ames). 

SPECTRA    OF   THE  ELEMENTS.  1 73 

ZIRCONIUM. 

The  visible  portion  of  the  spark-spectrum  has  been  meas- 
ured by  Thalen,1  who  passed  powerful  sparks  through  the 
chloride.  Lockyer  2  observed  twenty-three  lines  in  the  arc- 
spectrum  between  A  =  4000  and  3900. 

Spark-spectrum : 

6344.8   6311.3   6141.8   6133.7   6128.1   5350.5   5191.7 
4816.1   4772.1   4739.5   4710.5   4687.5   4155.7   4149.7 

1  N.  A.  S.  U."(i868)  [3]  6. 

2  P.  T.  (1881)  173,  561.      See  also  Troost  and  Hautefeuille,  C.  r.  (1871) 
73,  620. 


CHAPTER  VIII. 
ABSORPTION-SPECTRA. 

AN  attempt  to  treat  absorption-spectra  in  the  same 
systematic  manner  as  emission-spectra  is  attended  with  con- 
siderable difficulty.  The  latter  have  in  many  cases  been 
thoroughly  investigated,  and  all  the  lines  measured  on  a 
uniform  system  of  wave-lengths,  but  observations  of  the 
former  are  almost  exclusively  confined  to  the  visible  region, 
although  some  investigations  of  the  ultra-violet  and  infra-red 
regions  have  given  very  promising  results.  Many  of  the 
observations  have  been  made  by  the  help  of  instruments 
unprovided  with  measuring  appliances,  or,  when  these  were 
present,  only  arbitrary  scales  were  employed.  The  majority  of 
observers  omit  details  of  the  concentration  of  the  solutions, 
and  of  the  thickness  of  the  layer  of  liquid,  so  that  the  results 
plotted  as  curves  are  not  comparable  with  one  another.  Kriiss' 
method  of  determining  the  minimum  of  brightness  is  perhaps 
well  adapted  to  give  results  meeting  the  above  conditions,  but 
hitherto  it  has  not  been  generally  employed.  Some  of  the 
problems  which  have  arisen  during  the  later  development  of 
spectroscopic  work  should  be  capable  of  solution  by  the  study 
of  absorption-spectra,  but  this  can  only  occur  if  the  investi- 
gations are  conducted  on  a  totally  different  plan,  and  the 
greater  portion  of  the  work  hitherto  accomplished  must  be 
repeated.1 

1  Comp.  Hasselberg,  K.  Svenska.  Vetensk.  Akad.  Handl.  (1891)  24. 
No.  3. 

174 


ABSORPTION-SPECTRA.  1/5 

These  criticisms  are  not  intended  to  imply  that  the  study 
of  absorption-spectra  has  been  entirely  lacking  in  important 
results;  the  weighty  and  thorough  investigations  of  the  solar 
spectrum  which  belongs  to  this  class  of  spectra,  and  is  treated 
separately  in  the  following  chapter,  would  of  themselves  be 
sufficient  to  prove  the  contrary.  In  addition  numerous  im- 
portant observations  have  been  made  in  various  other  direc- 
tions; some  of  those  referring  to  inorganic  substances  arc 
mentioned  in  the  preceding  chapter.  In  the  majority  of 
instances,  although  the  results  have  some  value  as  preliminary 
observations,  they  lack  the  degree  of  accuracy  attainable  at 
the  present  time,  and  are  of  such  unequal  value  that  they 
can  scarcely  be  included  in  a  work  such  as  this,  where 
detailed  criticism  would  be  out  of  place,  whilst  the  redrawing 
of  curves  on  a  uniform  scale  instead  of  the  arbitrary  ones, 
would  introduce  fresh  sources  of  confusion  and  error. 

The  account  given  in  the  following  pages  will  be  restricted 
to  a  record  of  the  laws  deducible  from  the  results  of  observa- 
tions; further  details  can  be  obtained  by  consulting  the 
original  memoirs,  or  H.  W.  Vogel's  "  Praktische  spectral- 
analyse, "  Berlin,  1889,  which  contains  numerous  illustrations 
of  absorption-spectra. 

To  show  the  method  usually  adopted  for  the  graphic  re- 
cording of  the  results,  a  table  of  some  well-known  absorption- 
spectra  is  given  in  Fig.  41.  The  spectra  of  inorganic  com- 
pounds include  those  of  salts  of  chromium,  copper,  cobalt, 
iron,  manganese,  nickel,  and  uranium,  whilst  the  organic 
compounds  are  alizarin,  aniline  blue,  chlorophyll,  eosin, 
fluorescei'n,  fuchsin  (magenta),  indigo,  malachite  green, 
methyl  violet,  purpurin,  quinoline  red,  safranine,  and  blood 
in  aqueous  solution,  both  alone,  and  after  treatment  with 
reagents;  these  are  useful  for  the  identification  of  blood- 
stains, and  for  the  diagnosis  of  carbon  monoxide  poisoning. 

Absorption  by  Gases  and  Liquids. — The  laws  of  the 
absorption  by  gases  have  been  discussed  in  Chapter  VI.  The 


.     SPECTRUM  ANALYSIS. 


TABLE  OF  ABSORPTION-SPECTRA. 
C  D  Eb       F  G 


760 


1 

2 
3 
4 
5 
6 
7 
8 
9 

10 
11 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
22 
23 
24 
25 
26 
27 
28 
29 
30 
31 
32 


8 


Chrome  alum(violet)  inwater. 
Chrome  alum(green)  inwater. 
Ferric  chloride  in  water. 
Ferric  thiocyanate  in  ether. 
Cobalt  chloride  (solid). 
Cobalt  chloride  in  alcohol. 
Cobalt  chloride  in  water. 
Cupric  sulphate. 

Potassium  permanganate   in 

water. 
Potassium       manganate      in 

water. 

Nickel  chloride  in  water. 
Uranium  nitrate  in  water. 

Uranous  salt  m  water. 
»•> 
Alizarin  in  sulphuric  acid. 

Aniline  blue  soluble  in  water. 

Blood.     Oxyhaemoglobin. 

Blood.  Oxyhsemoglobm,  re- 
duced. 

Blood.  Haematin  in  hot  al- 
cohol. 

Blood.  Hsematm  in  cold  al- 
cohol. 

Blood.  Hsematin  in  alcohol 
and  ammonium  sulphide. 

Blood.  Carbon  monoxide 
haemoglobin. 

Quinoline  red  in  alcohol. 
Chlorophyll(fresh)  in  alcohol. 
Eosin  in  alcohol. 
Fluorescein  in  alcohol. 
Fuchsin  in  alcohol. 

Indigo  in  sulphuric  acid  or 
chloroform. 

Malachite  green. 

Methyl  violet. 

Purpurin  in  sulphuric  acid. 

Safranine  salt  with  i  equiv. 

of  acid. 
Safranine  salt  with  2  equivs, 

of  acid. 


B      0 


Eb 


FIG.  41. 


ABSORPTION-SPECTRA.  1 77 

absorption  by  liquids  differs,  as  Ostwald  1  has  shown,  accord- 
ing to  whether  or  no  the  substance  is  a  salt.  In  the  case  of 
colored  bodies  other  than  salts,  the  color  is  a  constitutive 
property,  as  is  well  exhibited  in  the  case  of  organic  dyes.2 
Every  change  in  the  molecule  produces  a  definite  alteration 
in  the  absorptive  power,  so  that  variation  in  the  absorp- 
tion is  correlated  with  change  in  the  molecular  condition 
(Stenger).  The  absorptive  power  of  salts  in  dilute  solution  is 
purely  additive,  and  is  the  resultant  of  the  sum  of  the  color 

of  the  ions. 

v 

Different  Salts  of  the  same  Colored  Base  or  Acid.— 

The  first  systematic  investigations  of  the  absorption-spectra 
of  different  salts  of  the  same  acid  were  made  by  Gladstone;3 
his  results  show  that,  in  general,  a  base  or  acid  retains  its 
absorptive  power  in  its  compounds.  Arrhenius'  electrolytic 
dissoci  tion  theory  indicates  that  aqueous  salt  solutions 
become  more  dissociated  as  the  dilution  increases,  until  a 
limit  is  reached  at  which  the  properties  become  wholly  addi- 
tive, and  are  the  sum  of  those  of  the  ions.  Ostwald  has 
tested  this  theory  by  an  examination  of  the  color  of  salt  solu- 
tions. The  absorption-spectrum  of  a  salt,  in  a  solution  of 
infinite  concentration,  would  be  rather  complex,  as  the  solu- 
tion would  contain  at  least  three  constituents,  viz.,  undecom- 
posed  molecules,  and  the  two  ions;  the  spectrum  would 
therefore  be  compounded  of  three  distinct  absorption-spectra, 
the  relative  intensity  of  which  would  be  proportional  to  the 
quantity  of  each  constituent  present,  and  the  undecomposed 
molecules  might  exist  in  aggregations  of  varying  degrees  of 
complexity.  With  this  property,  as  with  all  others,  increas- 


1  Ueber  die  Farbe  der  lonen.     Abhandl.  K.  sach.  Ges.  d.  Wissensch.  31. 
Zeitschr.  phys.  Chem.  (1889)  3,  601  ;  (1892)  9,  226,  579.     Compare  also  Mag- 
nanini,  Zeitschr.  phys.  Chem.  12,  56.     O.  Knoblauch,  W.  A.  (1891)  43,  738. 
Wagner,  Zeitschr.  phys.  Chem.  12,  314.     Ewan,  P.  R,  S.  (1895)  57,  117. 

2  Stenger,  W.  A.  (1888)  33,  577- 

3  P.  M.  (1857)  14,  418. 


178  SPECTRUM  ANALYSIS. 

ing  dilution  causes  simplification  as  the  molecular  aggregates 
are  resolved,  until  a  limit  is  attained  at  which  the  phenomena 
are  caused  solely  by  the  ions.  The  spectrum  of  a  highly 
dilute  salt  solution  is  therefore  the  sum  of  the  spectra  of  its 
ions.  The  matter  may  be  further  simplified  by  selecting 
compounds  with  one  colorless  ion,  i.e.,  one  that  exerts  no 
absorptive  power  on  the  particular  region  of  wave-lengths 
under  examination.  Hence  it  follows  that  in  highly  dilute 
solutions  compounds  of  a  particular  colored  ion  with  any 
colorless  ones  must  give  identical  absorption-spectra;  this  is 
in  accordance  with  Kundt's  rule,  and  apparent  exceptions 
appear  to  be  all  due  to  secondary  influences.  Ostwald  has 
photographed  the  absorption-spectra  of  about  300  salts, 
including  those  of  the  following  substances:  permanganic 
acid,  fluorescein,  eosin,  iodeosin,  tetrabromorcinolphthalei'n, 
dinitrofluorescei'n,  rosolic  acid,  diazoresorcinol,  diazoresorufin 
(resorufin),  chromium  oxalates,  safranines,  rosanilines,  aniline 
violet,  chrysaniline,  and  chrysoidin.  All  th^  compounds 
investigated  conformed  with  the  above  rule;  apparent  excep- 
tions were  observed  in  the  case  of  certain  feeble  acids  or 
bases,  the  salts  of  which  are  hydrolyzed,  but  the  addition  of 
excess  of  the  base  or  acid  overcame  this  divergence,  and  the 
behavior  of  the  solution  was  then  normal.  Some  salts  are 
insoluble,  and  therefore  not  dissociated;  these  also  are  appar- 
ent exceptions.  Occasionally  the  salt  forms  visible  deposits 
of  a  colloidal  nature,  but  if  the  dilution  prevents  this,  a 
determination  of  the  electrolytic  conductivity  will  immediately 
establish  the  absence  of  dissociation. 

Relationship  between  the  Molecular  Structure  and  the 
Absorption-spectrum. — Many  investigations  have  been  made 
to  determine  the  influence  of  chemical  composition  on  the 
position  of  the  absorption-bands;  a  number  of  regularities 
have  been  observed,  particularly  in  the  case  of  organic  com- 
pounds, but  no  law  of  general  applicability  has  been  formu- 
lated. 


ABSORPTION-SPECTRA.  179 

Absorption  in  the  Visible  Portion  of  the  Spectrum. — 
The  primary  object  of  the  earlier  workers  was  the  general 
investigation  of  the  spectra,  rather  than  their  relationship  to 
the  chemical  constitution  of  the  compounds.  The  chrysoidins 
were  the  first  dyes,  the  color  of  which  could  be  changed  at 
will  from  pale  yellow  to  red  by  the  systematic  introduction  of 
various  groups;  these,  and  other  azo-dyes  of  known  constitu- 
tion, were  examined  by  Landauer;1  the  spectra  obtained  were 
not  very  sharp,  but  it  was  shown  that  the  absorption-bands 
undergo  a  marked  change  when  the  hydrogen  in  the  amido- 
group  is  replaced  by  methyl.  G.  Kriiss  investigated  indigo  2 
and  fluorescem  3  derivatives,  and  arrived  at  the  following  con- 
clusions. The  substitution  of  hydrogen  by  methyl,  ethyl, 
methoxyl,  carboxyl,  or  any  group  which  increases  the  per- 
centage of  carbon  in  the  compound,  causes  the  absorption- 
bands  to  approach  the  red;  the  effect  of  bromine  is  similar. 
The  minima  of  brightness  approximate  towards  the  blue  if 
hydrogen  is  replaced  by  the  nitro-  or  amido-groups;  the  dis- 
placement increases  as  the  number  of  substituting  groups 
rises,  and,  if  the  groups  are  identical,  it  is  proportional  to 
their  number.  Kruss'  rule,  except  the  proportional  displace- 
ment, was  confirmed  by  Liebermann  and  Kostanecki 4  in  the 
case  of  methylated  hydroxyanthraquinones,  and  by  Bernthsen 
and  Goske  5  in  that  of  dimethyl-  and  diethylthionine.  The 
latter  workers  observed  that  the  introduction  of  two  methyl 
groups  produces  a  displacement  of  about  2Oyw//,  the  change 
caused  by  two  additional  methyl  groups  being  about  45/^u. 
E.  Vogel 6  subsequently  proved  that  the  proportional  displace- 
ment of  the  absorption-bands  is  the  exception  instead  of  the 

1  Ber.  (1881)  14,  391. 

2  G.  Kriiss  and  S.  Oeconomides,  Ibid.  (1883)  16,  2051. 

3  Ibid.  (1885)  18,  1426. 
*  Ibid.  (1886)  19,  2327. 

5  Ibid.  (1887)  20,  924.     See  also   Bernthsen,  Studium  in  der  Methylene- 
fclaugruppe.     Lieb.  Ann.  (1885)  230,  73.     Goske,  Inaug.-Diss.  Zurich,  1887. 

6  W.  A.  (1891)  43,  449. 


180  SPECTRUM  ANALYSIS. 

rule;  in  the  eosin  compounds  the  displacement  depends  both 
on  the  number  and  position  cf  the  substituting  groups.  In 
aqueous  solution  the  displacement  varies  according  to  whether 
the  substituting  group  enters  the  phthalic  acid,  or  the  resor- 
cinol  nucleus.  Influence  is  also  exercised  by  the  position,  in 
the  phthalic  acid  radicle,  of  the  substituting  group,  if  any, 
and  also  by  the.  solvent  employed.  H.  W.  Vogel 1  had 
previously  shown  that  the  extent  to  which  the  absorption- 
bands  are  displaced  is  intimately  related  to  the  position  of  the 
substituting  group  in  the  molecule.  He  investigated  methy- 
lated azo-dyes  in  concentrated  sulphuric  acid  solution. 
Grebe8  worked  on  the  same  subject,  and  examined  more  than 
a  hundred  azo-dyes;  his  conclusions  are  as  follows:  In  sul- 
phuric acid  solution  the  absorption-bands  of  the  azo-dyes 
approach  the  red  as  the  content  of  carbon  increases.  Hy- 
droxyl-  and  amido-groups  act  in  a  similar  manner;  constancy 
in  the  position  of  the  radicles  produces  a  constant  displace- 
ment of  the  bands;  thus  if  hydroxyl  is  introduced  into  the 
naphthalene  molecule,  the  ^-compounds  exhibit  bands  which 
are  always  about  2O//yu  nearer  to  the  red  than  those  of  the 
isomeric  ytf-derivatives.  The  sulphonic  group  produces  a  dis- 
placement in  the  opposite  direction;  it  is  almost  constant, 
and  approximates  to  4O/^w;  the  bands  are  more  clearly  defined, 
and  the  influence  of  the  position  of  the  group  is  also  nearly 
constant. 

In  connection  with  the  relationship  between  color  and 
absorption-spectrum  Schutze's3  theory  of  dyes  may  be  men- 
tioned. A  study  of  physics  shows  that  the  mixture  of  colors 
composing  the  solar  spectrum  appears  white  because  each 
color  has  an  equally  strong  complementary  color;  these 
neutralize  one  another,  arid  produce  on  the  eye  the  effect  of 
whiteness.  If  a  color  is  abstracted  from  the  spectrum  by 

1  Sitzungsber.  Berl.  Akad.  (1887)  34,  715.     Ber.  21,  7760. 

2  Zeitschr.  f.  phys.  Chem.  (1893)  10,  673.     Ber.  (1893)  26,  1300. 

3  Zeitschr.  f.  phys.  Chem.  (1892)  9,  109.     Meyer's  Jahrb.  1892,  p.  n. 


A  BSORP  TION-SPE  CTRA .  1 8 1 

absorption,  the  issuing  light  will  be  tinged  with  the  comple- 
mentary color.  Many  colorless  substances  exhibit  absorption- 
bands  in  the  ultra-violet;  the  introduction  of  groups  which 
displace  the  bands  towards  the  red  ("  catho-chromic  groups  ") 
first  produces  absorption  in  the  violet,  and  the  substance  con- 
sequently assumes  a  greenish  yellow  color.  "  Hypsochromic 
groups  "  displace  the  absorption-bands  towards  the  violet,  and 
their  introduction  causes  the  opposite  effect ;  such  groups  are 
not  numerous.  *  This  explanation  is  in  accord  with  the  em- 
pirical rule,  enunciated  in  1877  by  Nietzki,  which  states  that 
the  simplest  dyes  are  greenish  yellow  or  yellow;  as  the  molec- 
ular weight  increases,  the  color  changes  successively  to  orange, 
red,  violet,  blue,  and  green.  In  the  case  of  analogous 
elements  a  rise  in  the  atomic  weight  also  produces  an  increase 
in  the  depth  of  the  color;  an  example  is  furnished  by  the 
fluorine  group:  this  element  is  light  greenish  yellow,  chlorine 
is  a  deeper  greenish  yellow,  bromine  red,  and  iodine  violet. 
Experience  shows  that  the  color  of  many  organic  compounds 
is  dependent  on  the  presence  in  the  molecule  of  certain  groups, 
such  as  the  azo-group  in  the  azo-dyes;  this  suggests  that 
these  complexes  are  probably  the  active  agents  in  producing 
the  absorption  of  light  by  the  molecule,  and  that  change  in 
the  color  caused  by  substitution  is  due  to  influence  exerted 
by  the  substituting  radicles  on  these  groups.1  «  This  view  was 
first  developed  by  O.  N.  Witt,a  who  applied  the  term 
41  chromophore  "  to  the  group  producing  the  color  ;^since  the 
influence  of  a  substituting  group  on  the  chromophore  will  be 
stronger  the  nearer  their  positions  approximate  in  the  mole- 
cule, the  theory  affords  a  prospect  of  determining  the  relative 
distance  of  the  groups  by  spectroscopic  measurement. v  Schutze 
examined  certain  azo-dyes,  and  found  that  the  relative  dis- 
tance of  the  atoms  in  the  molecule  indicated  by  the  structural 

1  Compare  Hartley,  J.  Chem.  Socy.  (1887)  51,  152.     Ber.  (1887)  20,  131. 

2  Ibid.  (1876)  9,  522. 


1*2  SPECTRUM  ANALYSIS. 

formulae  of  the  compounds  corresponded,  on  the  whole,  with 
the  spectroscopic  measurements. 

Spring,1  using  extremely  thick  layers,  observed  that 
"colorless"  organic  compounds  exhibit  spectra  free  from 
absorption-bands  if  their  molecules  consist  of  carbon  chains 
about  which  the  heterologous  atoms  or  groups  are  equally  or 
symmetrically  divided.  Concentration  of  the  atoms  or  radicles 
at  one  end  of  the  chain  causes  the  appearance  of  absorption- 
bands.  The  number  of  the  bands  appears  to  be  directly 
related  to  the  number  of  the  hydrocarbon  radicles  present  in 
the  compound;  their  position  is  apparently  determined  by  the 
nature  of  each  group,  but  if  two  of  these  are  very  intimately 
linked,  the  combined  influence  causes  a  change  in  the  position 
of  the  corresponding  bands,  which  may  even  merge  into  a 
single  one. 

Absorption  in  the  Ultra-violet. — The  relationship  be- 
tween the  constitution  of  substances  and  their  absorption- 
spectra  in  the  ultra-violet  region  was  first  shown  by  Soret  and 
Rilliet,2  and  Hartley  and  Huntington.3  The  former  examined 
the  ethylic,  isobutylic,  and  amylic  salts  of  nitric  and  nitrous 
acids;  these  compounds  are  not  well  suited  to  investigations 
of  this  nature,  as  tne  absorption  is  confined  to  one  end  of  the 
spectrum,  and  does  not  include  measurable  bands,  but  their 
observations  rendered  it  probable  that  the  whole  absorption- 
field  is  displaced  towards  the  red  if  a  .  hydrogen  atom  is 
replaced  by  methyl.  Hartley  and  Huntington3  obtained 
more  definite  results,  showing  that  the  normal  fatty  acids 
have  a  stronger  absorptive  power  for  the  refractive  rays  of  the 
ultra-violet  region  than  the  corresponding  alcohols,  and  that 
increase  in  absorptive  power  in  this  part  of  the  spectrum  is 
correlated  with  increase  in  the  number  of  CH2  groups  in  the 
molecule  of  the  homologous  alcohols  and  acids. 

1  Bull.  Acad.  roy    Belgique  [3]  33,    165.     Chem.  Centralbl.  (1897)  68, 
1114. 

2  C.  r.  (1879)  89,  747. 

3  P.  R.  S.  (1879)  p.  233.     P.  T.  (1879)  170,  257. 


A  BSORP  TION-  SPECTRA .  183 

Hartley,1  partly  in  conjunction  with  Huntington,8  has 
carried  out  further  extensive  investigations  of  the  relationship 
between  the  absorption-spectra  of  carbon  compounds  and 
their  molecular  structure.  The  following  is  a  summary  of 
the  results:  The  alcohols  CnH2n  +  2,  ethers,  and  ethereal  salts 
(esters)  readily  transmit  the  ultra-violet  rays;  methyl  alcohol 
almost  as  completely  as  water;  but  the  fatty  acids  absorb  these 
rays  to  a  greater  extent  than  do  the  corresponding  alcohols. 
None  of  the  compounds  examined  exhibit  absorption-bands. 
In  the  case  of  the  alcohols  and  acids  the  absorption  increases 
as  the  content  of  carbon  in  the  compound  rises. 

Benzene  and  its  hydroxyl-,  carboxyl-,  and  amido-derivatives 
have  a  high  absorptive  power  for  the  ultra-violet  rays,  and  in 
thin  layers  exhibit  strong  absorption-bands.  The  spectra 
of  isomers  differ  both  in  the  position  of  the  bands  and  in  the 
extent  of  absorption.  In  the  cresols  and  dihydroxybenzenes 
the  meta-derivative  has  the  greatest,  and  the  para-compound 
the  least  absorptive  power,  but  orthoxylene  and  parahy- 
droxybenzoic  acid  absorb  more  light  than  the  isomeric 
compounds.  The  spectra  of  isomeric  terpenes  differ;  the 
compounds  C10H16  and  CJBH24  exceed  benzene  in  absorptive 
power,  the  former  to  a  greater  extent  than  the  latter.  Ab- 
sorption-bands are  confined  to  compounds  containing  ben- 
zenoid  carbon  linkages.  A  simple  linkage  of  carbon  and 
nitrogen  is  insufficient  to  produce  characteristic  absorption  of 
the  ultra-violet  rays.  The  substitution  of  a  nitrogen  atom  for 
a  CH  group  in  benzene  or  naphthalene  derivatives  (pyridine 
or  quinoline  compounds)  does  not  destroy  the  selective 
absorption-power,  but  this  disappears  if  the  benzenoid  linkage 
is  destroyed  by  combination  with  hydrogen.  The  addition 
of  four  atoms  of  hydrogen  to  carbon  atoms  in  the  quinoline 

1  J.   Chem.  Socy.  (1882);    (1885)  47,  685;    (1887)  51,   58;    53,  641.     Ber. 
(1885)  18,  592;  (1887)  20,  174;  (1888)  21,  689. 

2  P.  R.  S.  28,  233;  (1879)  29>  290;  (1880)  31,    i.     P.  T.  (1879)   170,  257. 
Ber.  (1881)  14,  501. 


1 84  SPECTRUM  ANALYSIS. 

molecule  only  diminishes  the  intensity  of  the  absorption- 
bands. 

Molecules  consisting  of  dissimilar  parts  vibrate  as  wholes. 
The  fundamental  vibrations  produce  secondary,  ones  which 
do  not  bear  any  recognizable  relationship  to  the  chemical 
constituents. 

Hartley  has  also  examined  the  carbohydrates  and  albumi- 
noids, and  has  investigated  the  physical  connection  of  these 
compounds  with  the  soluble  ferments.  The  spectra  of  egg 
albumin,  serum  albumin,  and  casein  exhibit  certain  bands  in 
common  which  are  absent  in  the  spectra  of  malt  diastase, 
yeast  invertase,  gelatin,  starch,  glycoses,  and  saccharose, 
solutions  of  which  are  particularly  transparent  to  the  violet 
and  ultra-violet  rays.  The  albumins  are  thus  shown  to  differ 
considerably  from  the  ferments  in  constitution,  and  this 
accords  with  the  difference  in  behavior  shown  by  the  com- 
pounds towards  carbohydrates. 

Absorption  in  the  Infra-red. — The  influence  of  the  atomic 
grouping  of  organic  compounds  on  their  absorption  of  the 
infra-red  rays  has  been  extensively  investigated  by  Abney 
and  Festing.1  Hydrogen  chloride  shows  a  few  lines,  water 
lines  and  bands;  ammonia,  and  nitric  acid  sharp  lines.  Many 
of  these  lines  coincide,  and  can  be  referred  to  hydrogen.  It 
is  to  some  extent  an  open  question  why  the  hydrogen  acts  as 
if  it  were  free,  and  produces  a  line-spectrum,  but  certain 
absorption-lines  exhibited  by  hydrocarbons  are  coincident 
with  some  shown  by  compounds  of  hyrdogen  and  oxygen,  or 
hydrogen  and  nitrogen,  which  are  known  to  be  due  to  hy- 
drogen. The  behavior  of  oxygen  varies  according  to  whether 
it  is  in  the  radicle;  if  it  links  radicles,  it  produces  a  continuous 
absorption  between  two  hydrogen  lines.  Oxygen  in  the 
radicle  increases  the  sharpness  of  the  bands,  and  causes  them 
to  be  bordered  by  lines. 

1  P.  R.  S.  31,  416;  (1881)  32,  258. 


ABSORPTION-SPECTRA.  185 

Organic  radicles  are  characterized  by  well-marked  band? 
which  chiefly  occur  between  about  700^  and  looo/*/*;  some 
have  a  distinct  absorption  at  about  7OOjw/*,  and  a  second  in 
the  neighborhood  of  900;^,  but  the  characteristic  absorption 
of  the  radicle  is  almost  always  in  the  former  region.  The 
ethyl  group  has  an  absorption  at  742 /f/u,  and  a  characteristic 
band  between  892///t  and  92O/*/u.  The  characteristic  line  of 
the  phenyl  group  is  at  867/*//.  A  comparison  of  the  spectra 
of  ammonia,  benzene,  aniline,  and  dimethylaniline  shows  a 
very  close  coincidence,  and  proves  how  slight  an  effect  is  pro- 
duced by  varying  the  mass  of  the  radicles  linked  to  the 
nitrogen  atom.  Abney  and  Festing  were  unable  to  demon- 
strate the  presence  of  haloids  in  organic  compounds  by  means 
of  their  absorption-spectra  in  the  infra-red. 


CHAPTER    IX. 
THE   SOLAR  SPECTRUM. 

The  Fraunhofer  Lines — The  solar  spectrum  is  the  most 
complex  of  all  absorption-spectra.  It  is  permeated  with  a 
number  of  vertical  lines  which  were  first  observed  by  Wollas- 
ton  1  in  1802,  and  investigated  by  Fraunhofer,8  after  whom 
they  are  named.  He  prepared  a  drawing  of  the  spectrum, 
which  is  reproduced  in  Fig.  42,  and  contains  about  350  lines. 
The  more  prominent  are  designated  by  the  Latin  letters  A  to 
H.  By  means  of  accurate  measurements  Fraunhofer  showed 
that  the.  lines  are  constant  both  in  relative  position  in 
the  spectrum,  and  also  in  mutual  distance.  He  observed 
that  the  spectra  of  the  moon  and  planets  are  identical  with 
that  of  the  sun,  but  differ  from  those  of  Sirius  and  other  fixed 
stars,  so  that  the  lines  must  originate  in  the  sun  and  fixed 
stars,  and  not  in  the  earth's  atmosphere.  In  1824  he  proved 
the  coincidence  of  the  double  ZMine  of  the  solar  spectrum 
with  that  of  the  sodium-spectrum,  but  was  unable  to  explain 
the  origin  of  the  dark  lines.  Nine  years  later  Brewsfer1 
found  that  when  the  sun  is  low,  so  that  the  light  traverses  a 
considerable  thickness  of  atmosphere,  new  lines  become  visi- 
ble; these  are  produced  by  atmospheric  absorption,  and  were 
first  accurately  mapped  by  Brewster4  alone,  and  in  conjunc- 
tion with  Gladstone.5  Angstrom  and  others  almost  succeeded 

1  P.  T.  1802,  p.  365. 

2  Denkschr.  d.  Miinchener  Akad.  1814-15. 
«  P.  T.  E.  1833. 

4  P.  M.  [3]  8,  384.     P.  A.  (1836)  38,  50. 

5  P.  T.  (1860)  150,  149 

1 86 


THE   SOLAR   SPECTRUM. 


I87 


Red 

Orange 
Yellow 

Green 
Blue 

Indigo 


Violet 


FIG.  42. 


1 88  SPECTRUM  ANALYSIS. 

in  showing  the  origin  of  the  lines,  and  this  was  finally  accom- 
plished by  Kirchhoff1  in  1859,  as  a  consequence  of  the  law  of 
exchanges  which  he  had  recently  formulated  (comp,  Chapter 
VI).  The  explanation  of  their  origin  offered  a  prospect  of 
determining  the  composition  of  the  sun  and  fixed  stars,  so 
that  they  at  once  received  considerable  attention.  It  became 
necessary,  therefore,  to  measure  the  position  of  the  Fraunhofer 
lines,  and  also  those  in  the  spectra  of  the  elements,  with  a 
greater  degree  of  accuracy  than  had  been  hitherto  attained; 
this  was  done  by  Kirchhoff.2  who  used  a  prism  spectroscope, 
and  consequently  an  arbitrary  scale.  Angstrom,  in  the  prep- 
aration of  his  atlas  of  the  solar  spectrum  which  appeared  in 
1868,  made  the  measurements  in  wave-lengths,  and,  like 
Fraunhofer,  employed  diffraction  gratings.  His  normal  spec- 
trum included  about  1000  lines,  all  based  upon  wave-lengths, 
and  the  atlas  remained  the  foundation  of  all  wave-length 
determinations  for  more  than  twenty  years.  The  accuracy  of 
his  work  was  scarcely  exceeded  by  the  more  extensive  charts 
of  H.  C.  Vogel  and  Muller,3  Fievez,4  Piazzi-Smyth,6  Thollon,6 
and  Young.  Mascart,7  Draper,8  and  Cornu9  have  investigated 
the  ultra-violet  region  of  the  solar  spectrum;  the  scale  of  the 
chart  and  the  wave-lengths  of  the  last  observer  correspond 
with  those  of  Angstrom.  Abney  10  photographed  the  infra-red 
region,  and  used  his  own  special  plates,  which  are  sensitive  to 

Monatsber.  Berl.  Akad.  V.  27,  Oct.  1859. 

A.  B.  A.  1861. 

Publicationen  des  Astrophys.  Obs.  zu  Potsdam  (1879),  1. 

Annales  de  1'Observatoire  Royal  de  Bruxelles  (1882)  [3],  4;  (1883)  5. 

T.  R.  S.  E.  (1880)  29,  285;  32,  37,  233,  519. 

C.  r.  88,  80.     Ann.  de  1'Observ.  de  Nice  (1890),  3. 

Ann.  de  1'Ecole  normale  sup.  (1864)  1. 

Sillim.  Jour.  1873.     P.  A.  (1874)  151. 

C.  r.  86,    101,    315,    530.     Ann.  de   1'Ecole    norm.   [2]   3,  421;    9,   21. 
Spectre  normal  du  soleil  (Paris,  1881). 

10  P.  M.  [5]  6,  154;  11,  300.  P.  T.  (1880)  171,  653:  (1886)  177.  W.  A. 
Beibl.  4,  375;  5,  507,  509.  Abney  and  Testing,  P.  R.  S.  35,  80,324.  W.  A. 
Beibl.  8,  507. 


THE   SOLAR   SPECTRUM.  189 

these  rays.  The  spectrum  was  at  first  obtained  by  means  of 
prisms,  but  subsequently  with  a  Rowland's  concave  grating. 
Lommel1  has  also  photographed  the  infra-red  Fraunhofer 
lines,  and  Langley  3  has  investigated  them  by  means  of  the 
bolometer  (comp.  Chapter  V).  Mascart  and  Cornu  extended 
Fraunhofer's  designation  of  the  lines  by  Latin  capitals  up  to 
U  '=  2948  Angstroms,  and  Abney  introduced  the  following 
signs  for  the  infra-red: 


^  I  27000  Y\ 

W,  \  Z70C  *  \  8986.5  X,  8497.0        Calculated  on 

$t     12400  X,   8806.1  z     g2  |    Angstrom's  scale. 

#!     12000  X3   8661.4  J 

After  Angstrom's  death  it  was  found  that  his  determina- 
tions were  about  ^lAnr  to°  small  in  consequence  of  his  having 
used  an  incorrect  metre-scale,  so  that  new  and  more  exact 
wave-length  measurements  became  necessary.  Muller  and 
Kempf3  made  careful  investigation  of  300  solar  lines,  and 
almost  simultaneously  Rowland,  in  1886,  published  the  first 
edition  of  his  photographic  atlas  of  the  normal  solar  spectrum. 
A  superior  and  more  complete  edition4  appeared  in  1889. 
It  consists  of  ten  tables,  each  measuring  3X2  feet,  and  con- 
taining two  spectrum  sections.  It  includes  the  region  between 
3000  and  6950  Angstroms,  and  the  scale  which  is  attached  is 

o 

correct  to  within  less  than  0.05  Angstrom.  Photographs 
which  are  made  by  the  sun  itself  are  obviously  superior  to 
charts  prepared  by  drawing  and  measurements.  As  an  appen- 
dix to  the  atlas,  Rowland  6  has  published  a  table  of  the  wave- 
lengths of  numerous  solar  and  metallic  lines,  the  results  of  ten 
years'  observations;  they  have  been  determined  by  his  coinci- 

1  Comp.  Chap.  V. 

2  Sillim.  Journ.  [3]  25;  28;  31;  (1886)  32;   (1888)  36;    (1889)  38.     W.  A. 
(1883)  19,  226,  384;  (1884)  22.     Beibl.  9,  335. 

*  Publicat.  d.  Astrophys.  Obs.  zu  Potsdam  (1886)  5. 

4  Photographic   map  of   the  normal  solar  spectrum.      Baltimore,  Md., 
Johns  Hopkins  Press.     The  price  of  the  tables  is  $2.50,  or  $20  the  set. 

5  Astronomy  and  Astrophysics  (1893),  12,  321.     P.  M.  (1894)  [5]  36,  49. 


1 90  SPE  CTR  UM  A  NA  L  YSIS. 

o 

dence  method,  and  are  exact  within  o.oi  Angstrom;   in  many 

o 

instances  the  accuracy  is  within  o.ooi  Angstrom,  i.e.,  I  in 
5,ooo,ooo.1  The  value  2)l -=  5896.156  is  taken  by  Rowland 
as  the  basis  of  his  tables  (comp.  Chapter  VII). 

An  exact  knowledge  of  the  position  of  the  solar  lines  is  of 
the  greatest  importance  for  the  orientation  of  spectra,  and  for 
the  determination  of  the  constituents  of  the  sun;  therefore  in 
the  following  table  Rowland's  measurements  of  the  Fraun- 
hofer  lines  are  reproduced  in  full.  The  letter  preceding  a 
line  is  the  one  in  general  use  for  its  designation;  chemical 
symbols  following  it  indicate  the  element  with  a  line  of  which 
it  coincides.  A  query  (?)  after  the  symbol  means  that  it  is 
doubtful  whether  the  line  does  belong  to  the  spectrum  of  the 
element.  Two  symbols  after  a  line,  such  as  3295.957  Mn-Di, 
implies  that  both  elements  have  a  coincident  line  of  this  wave- 
length. Two  or  more  symbols  in  brackets  show  that  a  line 
of  the  first  element  corresponds  with  one  side  of  the  solar  line, 
one  of  the  second  with  its  middle,  etc.  Lines  which  do  not 
coincide  with  those  of  any  known  element  are  followed  by  a 
query,  whilst  those  due  to  absorption  by  atmospheric  oxygen 
or  moisture  are  designated  by  atm.  (O)  or  atm.  (H2O).  All 
the  wave-lengths  are  given  in  Angstrom  units,  reduced  to  air 
at  20°  C.,  under  a  pressure  of  760  mm. 

The  Chemical  Composition  of  the  Sun. — The  establish- 
ment of  KirchhofTs  law,  and  the  experimental  reversal  of  the 
sodium  lines  (comp.  Chapter  VI)  naturally  directed  attention 
to  the  elucidation  of  the  composition  of  the  sun.  KirchhofTs 
careful  drawings  of  spectra  were  prepared  for  the  purpose  of 
comparing  the  position  of  solar  and  metal  lines.  He  employed 
the  Fraunhofer  lines  for  the  orientation  of  metallic  lines,  and 
found  that  the  iron  lines  coincided  exactly  with  similar  dark 
lines.  That  the  coincidence  of  only  sixty  lines  should  be  a 


1  A  list  of  the  lines  in  Rowland's  tables  has  appeared  in  the  Astrophys. 
Jour,  from  1895  onwards. 


THE   SOLAR    SPECTRUM.  19! 

ROWLAND'S  TABLE  OF  WAVE-LENGTHS  OF  THE  FRAUNHOFER 

LINES. 

Based  on  £>i  =  5876.156  Angstroms,  and  reduced  to  air  at  20°  and  760  mm. 

pressure. 


| 

3005.160 
3005.404 

p 
p 

3134.223 
3I37.44I 

Ni 
Co 

3377.667 

Ti) 
Tif 

3012.557 

p 

3140.869 

Fe 

3389.887 

Fe 

3014.274 
3016.296 

j 

Fe 

3J53.870 
3158.988 

Fe 
Ca 

3405.272 

Co) 
Ti  f 

3024.475 

? 

3167.290 

Mn 

3406.581 

Fe 

3025.394 

p 

3172.175 

Fe? 

3406.955 

Fe 

3025.958 

Fe 

3176.104 

La? 

3425.721 

? 

3035.850 

•) 

3188.164 

Cr? 

3427.282 

Fe 

3037.492 

Fe 

3195.702 

Ni 

3440.759 

Fe 

3044.119 

Ca[?Co] 

3200.032 

Ti 

"O]  3441.  135 

Fe 

3044.683 

Mn 

3214.152 

Fe 

3444.032 

Fe 

3046.778 

p 

3218.390 

Ti 

3455.384 

Co 

3047.720 

Fe 

3219.697 

Fe 

3464.609 

Sr? 

3050.212 
3053-I73 

3053-527 

j 

Fe 

? 

3219.909 
3222.203 

Fe 
Fe??[ 

3465.991 
3475.594 

Co) 
Fef 
Fe 

3055-821 

p 

3224.368 

Ti 

3476.831 

Fe 

3057.557 

Fe 

3225.923 

Fe 

Co) 

3059.200 

Fe 

Ti) 

3478.001 

Fe  V 

3061.098 

? 

3231.421 

?  I 

Nij 

3061.930 

Co 

3232.404 

Ti 

3486  036 

Ni 

3067.363 

Fe 

3236.697 

Ti 

3490.721 

Fe 

3075.339 
3075.849 

Ti 
Fe 

3246.124 

u 

3491.464 

c°\ 

3077-216 

Fe 

3247.680 

Cu 

3497.264 

Fe 

3077-303 
3078.148 

p 
Fe? 

3260.384 

Mn  ) 
Ti 

3497-991 

t\ 

3078.759 

Ti 

Fe    ) 

3500.721 

Fe 

3079.724 

Mn 

3267.839 

V 

3500.993 

Ni 

3080.863 

p 

3274.092 

Cu 

3510.987 

Ti 

3082.272 

Al 

3287.791 

Ti 

3513.947 

Fe 

3083.849 
3086.891 

Fe 

p 

3292.174 

Fe       ) 
Co-T  f 

•    3518.487 
3521.404 

Co 
Fe 

3088.137 

Ti 

3295.957 

Mn-Di 

3540.266 

Fe 

3092.824 

Al 

3302.501 

Na 

3545-333 

p 

3092.962 

Al 

3303-107 

Na 

3549-145 

Yt 

3094.739 
3095.003 

? 
Fe 

3303-648 

4 

3550.006 
3558.670 

Fe 
Fe 

3100.064 
3100.415 

Fe 
Fe(Mn) 

3306.117 
3306.471 

Fe 
Fe 

3564.680 

Ti) 
Fef 

3100.779 
3101.673 

Fe 

Ni 

3308.928 

Mn       ) 
Co-Ti  f 

3565.528 
3570.225 

Fe 
Fe 

3101.994 

Ni 

3318.163 

Ti 

3570.402 

Fe 

3106.677 

? 

333L74I 

Fe 

N]  3581.  344 

Fe 

3109.434 
3115.160 

Cr? 

Fe 

3348.011 

Cr) 
Fe  f 

3583-483 
3584.662 

Fe? 
Yt 

3121.275 

V 

3351.877 

Fe 

3585.992 

C 

3129.882 

Zr 

3356.222 

Zr 

3586.041 

C 

1 92 


SPECTRUM  ANALYSIS. 
ROWLAND'S    TABLE.— Continued. 


3590.523 

3597-I92 

C 

Fe 

3736.969 

Ni    ) 
Mn  ) 

3883.773 

3886.427 

Cr 
Fe 

3600.880 

Yt(Fe) 

3737-075 

Ca 

3897.599 

Fe 

3602.061 

Yt 

3737.282 

Fe 

3905.666 

Si 

3605.483 

Cr 

Ti) 

3916.875 

Fe 

3605.635 

Fe 

3743-502 

Fer 

3924.669 

Ti 

3606.831 
3609.015 

Fe 
Fe 

3745.701 

Cr) 
Fe 

3925-345 

Fe) 
V    f 

3611.193 

Yt 

3746.054 

Fe 

3925.792 

Fe 

3612.217 

Fe 

fa   ) 

3747-095 

Fe  ) 

3926.123 

F?e  !• 

3617.92° 

*~"*      f 

Fef 

3748.409 

Fe 

3928.071 

Fe 

3618.924 

Fe 

3749.633 

Fe 

KJ3933  809 

Ca 

3621.122 
3621.606 

Yt 
Fe 

3754.664 

l\ 

3937-474 
3941.021 

Fe 

Fe-Co 

3622.147 

Fe 

3756.2H 

Fe 

?    i 

3623.332 

Fe 

3758.379 

Fe 

3942.559 

Fe  f 

3623.603 

Fe 

3763.942 

Fe 

3944.159 

Al 

3628.853 

Yt 

3767.344 

Fe 

3949.C34 

Ca 

3631.619 

Fe 

3770.130 

Fe 

3950.101 

Fe 

3633.259 

Yt 

3774.480 

Yt? 

3950.497 

Yt 

3635-616 

Ti 

3780.846 

? 

3954.001 

Fe 

3638.435 

Fe 

3781.330 

Fe 

3957.i8o 

Fe-Ca 

3640.536 

Cr  ) 

3783-674 
3788.032 

Ni 
Fe 

3960.429 
3961.676 

Fe 
Al 

3647.995 

Fe 

3794-014 

Fe-Cr 

HJ3968.620 

Ca 

3652.692 

Co 

3795-150 

Fe 

397I-478 

Fe 

3653.639 

Ti 

3798.662 

Fe 

3973.835 

Ca 

3658.688 

Mn) 
Fe    f 

3804.153 

Fe 
Fe 

3977.89I 
3981.914 

Fe 
Fe-Ti 

3667.397 
3680.064 

Fe 

Fe 

3805.487 
[L]  3815.985 

Fe-Di 
Fe 

3984-078 

Cr) 

Fe  f 

3683.202 

Co) 
Fe[ 

3820.567 

3821.318 

Fe 
Fe 

3986.903 

Mn  [ 

v  ) 

3823.651 

Mn(Cr) 

?    j 

3683.622 

Pb 

3826.024 

Fe 

3987.216 

Mn  I 

3684.259 

Fe 

3827.973 

Fe 

Co   ) 

3687.607 

Fe 

3829.505 

Mg 

4003.916 

Ce-Fe-Ti 

3694-349 

Yt 

3832  446 

Mg 

4005.305 

Fe-? 

3695-194 

Fe 

3836.226 

?-C 

4016.578 

Fe 

3705-711 

3707.186 

Fe 
Fe 

3836.652 
3838.430 

C 

Mg 

4029.796 

Fe) 
Zr\ 

3709.397 

Fe 

3840.584 

Fe 

4030.914 

Mn 

3710.438 

Yt 

3843.406 

Fe 

4033.225 

Mn 

3716.585 

Fe 

3856.517 

Fe 

4034-641 

Mn 

3720.086 

Fe 

3860.048 

Fe 

.  4035.88 

Mn 

3722.691 

Ni        ) 
Fe-Ti  f 

3864.441 
3871.528 

C 
C 

4044.293 
4045.975 

K 
Fe 

[M]3727-763 
3732.542 

Fe 
Fe 

3875.224 

vj- 

4048.893 

Mnl 

3733-467 

Fe 

3883.472 

C 

Crn\ 

3735.014 

Fe 

3883.548 

C 

4055.701 

Mn 

THE   SOLAR   SPECTRUM. 
ROWLAND'S    TABLE.— Continued. 


T-93 


4062.602 
4063  756 

Fe 
Fe 

Nil 
4359-778          Cr  \ 

4691.581 

Ti  ) 
Fef 

4071.904 

Fe 

Zr) 

4703.180 

Mg 

4073.920 

Fe 

4369.943            Fe 

4703.986 

Ni 

4077.883 

Sr 

4376.103 

Fe 

4714.599 

Ni 

4083.767 

Fe    ) 
Mn  f 

[d]  4383.721 

Fe 
Fe  ) 

4722.349 

Zn 
Fe    ) 

4083.928 

Fe 

4391.149 

Tif 

4727.628 

Mn  f 

4088.716 

Fe 

4404.927 

Fe 

4754-226 

Mn 

4103.121 

Si     \ 
Mn  | 

4407-850 

V    ) 
Fe  f 

4783.601 

Mn 

?  ) 

4107.646 

Fe 

4413-181 

Cd 

4805.253 

Tif 

4114.600 

Fe 

4415.299 

Fe 

4810.723 

Zn 

4121.481 

Cr) 
Co) 

4425.609 
4435.132 

Ca 
Ca 

4823.697 
4824.325 

Mn 
Fe? 

4121.968 

Fe-Cr 

4435.852 

Ca 

4859.934 

Fe 

4157.948 

Fe 

4447.899 

Fe 

T]  4861.496 

H 

4185.063 

Fe 

4454.950 

Ca 

4890.945 

Fe 

4197.251 

C 

4456.047 

Ca 

4900.098 

Ti 

4199.263 

4202.188 
4215.616 

Zr) 
Fef 
Fe 
Fe) 

4456.793 
4494-735 

4497.041 

Ca 
Fe 

Cr) 
Zr  f 

4900.  306 
4903-488 
4919.183 

Yt 
Cr) 

Fef 

Fe 

4215-667 

f 

4499.070 

Mn  ) 

4920.682 

Fe 

4215.687 

Sr) 

4499  315 

?    \ 

4924.109 

Fe 

4216.137 

C 

4501.444 

Ti 

4924.955 

Fe 

4222.381 

Fe 

4508.456 

Ti? 

4934.247 

Ba 

[g]  4226  892 

Ca 

4554-213 

Ba 

4957.482 

Fe 

4250.290 

Fe 

4563.939 

Ti 

4957.786 

Fe 

4250.956 
4254.502 

Fe 
Cr 

457L277 
4572.157 

#  i 

4973-274 

TO 

Fcf 

4260.638 
4267.958 
4271.924 

Fe 

rU 

Fe 

457,8.731 
4588.384 
4590.129 
4602.183 

Ca-Ti 
Cr? 
Ti? 

Fe 

4978.782 
4980.362 

?  ) 
Fef 

"?} 

4274  958 

Cr 

4607.509 

Sr 

4981.915 

Ti 

4283.170 
4289.523 

Ca 
Ca 

46H.453 

£1 

4994.316 
4999.693 

Fe 
Ti-La 

4289.881 
.4293.249 

Cr 

? 

4629.515 

SI 

5005.904 
5006.303 

Fe 
Fe 

4299.152 
4302.689 

Ca 
Ca 

4637-683 
4638.194 

Fe 
Fe 

5007.431 

Ti  ) 
Fef 

4305.636 
4306.071 

Sr 
Ti 

4643.645 
4648.835 

Fe 

Ni 

5014.422 

(Ni)Ti  ) 

Ti  r 

4307.904 
[G]  4308.034 
4308.071 

Cal 

Fe} 

4668.303 
'4678.353 

il 

Cd 

'  5020.210 
5036.113 

Ti 
Ti^ 

Nif 

4318.818 

Ca 

4679.028 

Fe 

5041.795 

Ca 

[f]   4325  940 

Fe 

4680.319 

Zn 

5050.008 

Fe 

4343.387 

Cr) 
Fej 

4683.743 
4686.395 

Fe 

Ni 

5060.252 
5064.833 

Fe 
Ti 

4352.903 

Fe 

4690.  324 

? 

5068.946 

Fe 

I94 


SPECTRUM  ANALYSIS. 
ROWLAND'S    TABLE.  —  Continued. 


5083.525 

Fe 

5217.559 

Fe 

5383.576 

Fe 

5090.959 

Fe 

5225.690 

Fe 

5389.683           Fe 

5097.  1  76 

Fe 

5230.014 

Fe 

5393.378  '         Fe 

5105.719 

Fe(Cu) 

5233.124 

Fe 

5397.346           Fe 

5109.825 

Fe 

5242.662 

Fe 

5405.987            Fe 

?  ) 

5250.391 

Fe 

5410.000           Cr 

5110.570 

5115.558 

Fe? 

Ni 

5250.825 
5253.649 

Fe 
Fe 

Fe  / 

5415.421         y    j- 

5121.797 

Ni  ) 
FP  \ 

5260.557 

Ca 

Ca  ) 

5424.284  |       pe  j- 

5126.369 

re  j 
Co 

5261.880 

^,0.     1 

Crf 

5434.742            Fe 

5127.530 

Fe 

5262.341 

?    I 

5447.130           Fe 

Fe) 

5262.391 

Caj^ 

5455-666         Fe?  ) 

5133-871 

?  r 

5264.327 

Cr 

5455-759 

5139.437 

Fe) 

5264.371 

f 

5455-826         Fe    ) 

5139-539 

I 

5264.395 

Ca) 

5462.732  :         Ni 

5139.645 

Fe  ) 

5265-727 

Ca      1 

5463.174           Fe 

5141.916 

Fe 

5265.789 

I 

5463.493           Fe 

5142.967 

5143.042 

Ni[ 

5265.884 

(Ni?)  j 
Cr      J 

5466.608           Fe 

5477.128  ;         Ni 

5143.106 

Fe  ) 

5266.729 

Fe 

5487.968 

Fe 

5146.664 

Nij 

[E2]  5269.722 
5270.448 

Fe 

5497-731 
5501.685 

Fe 
Fe 

5151.026 

Fe    )- 
Mn  f 

[E,]  5270.495 
5270.533 

Fe) 

5507.000 
5513.207 

Fe 
Ca 

5154-237 

Ti?Co? 

5273.344 

Fe) 

5528.636 

Mg 

5155.937 

Ni 

5273-443 

\ 

5535.073 

Fe 

5159.240 

Fe? 

5273-554 

Fe) 

5543.418 

Fe 

5162.448 

Fe 

?    } 

5544.158 

Fe 

5165.190 

C 

5276.205 

Cr  V 

5555.113 

Fe 

5165.588 

Fe 

Co  ) 

5569.848 

Fe 

5167.501 

Mg) 

5281.968 

Fe 

5576  319 

Fe 

[b4]5i67.572 

V 

5283.803 

Fe 

5582.195 

Ca 

5167.686 

Fe    ) 

5288.708 

Fe 

5588.980 

Ca 

5169.066 

Fe  ) 

5296.873 

Cr 

5590.342 

Ca 

[b3]5i69.i6i 

V 

5300.918 

Cr 

5594.695 

Ca 

5169.218 

Fe) 

5307.546 

Fe 

5598.555 

Fe 

5171-783 

Fe 

5316.790 

Fe?) 

5598.715 

Ca 

[b2]5172.871 

Mg 

[147415316.870 

[• 

5601.501 

Ca 

5173-912 

Ti 

5316.950 

Co?) 

Fe) 

[b!]5183.792 

Mg 

5324-373 

Fe 

5603.097 

Ca}. 

5188.863 

Til 

5333.092 

Fe? 

Fe) 

5188.948 

[ 

5349.623 

Ca 

5615.526 

Fe 

5189.020 

Ca) 

5353-592 

Fe-Ni 

5615.879 

Fe 

5193.139 

Ti 

5361.813 

? 

5624.253 

Fe 

5198.885 

Fe 

5363-011 

Fe(Co)  ) 

5624.768 

Fe-V 

p   ) 

5363.056 

?    r 

5634.167 

Fe 

5202.483 

Fe  \ 

5367-670 

Fe 

5641.661 

Fe 

5204.  708 
5210.556 

Cr) 
Fef 
Ti 

5370.165 
5371.686 

Fe 
Ni        ) 
Fe-Cr  f 

5645.835 
5655.707 

5658.096 

Si 
Fe 
Yt? 

5215.352 

Fe 

5379.776 

Fe 

5662.745 

Fe 

THE   SOLAR   SPECTRUM. 
ROWLAND'S    TABLE.— Continued. 


195 


5675.648 
5679.249 

Ti 
Fe 

5930.410 

5934.883 

Fe 
Fe 

6256.574 

Ni) 
Fef 

5682.861 

Na 

5948.761 

Si 

6261.316 

Ti 

5688.434 

Na 

5956.925 

Fe 

6265.347 

Fe 

5701.769 

Fe 

5975.576 

Fe 

6270.439 

Fe 

5708.620 

Si 

5977-005 

Fe 

a]  6278.289 

atm.  (O) 

5709.616 

Fe 

5977.254 

atm.  (HaO) 

6281.374 

atm.  (O) 

5709.760 

Ni 

5985.044 

Fe 

6289.608 

atm.  (O) 

5711.318 

Mg 

5987.286 

Fe 

6293.152 

atm.  (O) 

5715-309 

Ni    ) 
Fe-Ti  f 

6003.245 
6008.196 

Fe 
Fe 

6296.144 
6301.719 

atm.  (O) 
Fe 

5731-973 

Fe 

6008.782 

Fe 

6314.874 

Ni 

5742-°66 

Fe 

6013.717 

Mn 

6315-541 

Fe 

5752.257 

Fe 

6016.856 

Mn 

6318.242 

Fe-(Ca) 

5753-342 

Fe 

A/~\OO    1A*7 

?    ) 

6322.912 

Fe 

5754.884 

Ni| 

W4U.  Jif/ 

6022.017 

Mn 

6335.550 
6337.042 

Fe 
Fe 

5763-215 

Fe 

6024.280 

Fe 

6344.370 

Fe 

5772.360 

Si 

6027.265 

Fe 

6355.259 

Fe 

5775.304 

Fe 

6042.316 

Fe 

6358.902 

Fe 

5782.346 

Cu?  Co? 

6056.232 

Fe 

6378.461 

Ni 

5784-081 

Cr 

6065.708 

Fe 

6380.951 

Fe 

5788.136 

Cr 

6078.709 

Fe 

6393.818 

Fe 

Cr) 

6079.223 

Fe 

6400.200 

? 

5791.207 

Fef 

6102.408 

Fe 

6400.  509 

Fe 

5798.087 

? 

Ca) 

6408.231 

Fe 

5798.400 

Fe 

6102.941 

Fef 

6411.864 

Fe 

5805.448 

Ni 

6103.449 

6420.171 

Fe 

5806.954 

Fe 

6108.338 

Ni 

6421.569 

Fe 

5809.437 

Fe 

6111.287 

Ni 

6431.063 

Fe 

5816.594 

Fe 

6116.415 

Fe 

6439.298 

Ca 

5831.832 

Ni 

6122.428 

Ca 

6450.029 

Ca 

5853-903 
5857-672 

Ba 
Ca 

6136.834 
6141.934 

Fe 
Fe-Ba 

6462.835 

Ca) 

Fef 

5859.810 

Fe 

6154.431 

Na 

6471.881 

Ca 

5862.580 

Fe 

6160.970 

Na 

6480.264 

atm.  (H2O) 

[0315875.982 

He 

6162.383 

Ca 

•6482.099 

? 

5884.048 

Fe       ) 
at.  (H,0)  \ 

6169.260 
6169.775 

Ca 
Ca 

6494.001 
6495.209 

Ca 
Fe 

5889.854 

atm.  (H2O) 

6173-554 

Fe 

6499.871 

Ca 

[D,]5890.182 

Na 

6177.028 

Ni 

6516  315 

7 

5893.098 

Ni 

6180.419 

Fe 

6518.594 

Fe 

[D,]5896.154 

Na 

6191.397 

Ni 

6532.546 

atm.  (H2O) 

5898.395 

at.  (H20)) 
Fe?      \ 

6191.770 
6200.533 

Fe 
Fe 

6534.173 

Ti  ) 

5901.681 

at.  (HaO)  j 
Fe?      f 

6213.646 
6219.493 

Fe 
Fe 

6546.486 
6552.840 

Fef 
atm.  (H2O) 

5905.895 

Fe 

6230.946 

Fe-V 

;C]  6563.  054 

H 

59T4  384 

Fe       ) 
?-at.(H,0)$ 

6237.529 
6246.530 

7 
Fe 

6569.461 
6572.312 

Fe 
atm.  (H2O) 

5916.475 

Fe 

6252.776 

Fe 

6574.477 

p 

59I9-855 

atm.  (HaO) 

6254.454 

Fe 

6575.179            Fe 

1 9o 


SPECTRUM  ANALYSIS. 
ROWLAND'S  TABLE.— Continued. 


6593.161 

Fe 

6889.194 

atm.  (O) 

7148.427 

? 

6594.115 

Fe 

6890.  149 

atm.  (O) 

7168.191 

p 

6609.354 

Fe 

6892.614 

atm.  (O) 

7176.347 

at.  (H2O)? 

6633.992 

Fe 

6893-559 

atm.  (O) 

7184.781 

at.  (H2O?) 

6643.882 

Ni 

6896.292 

atm.  (O) 

7186.552 

at.  (H20^> 

6663.525 

p 

6897.195 

atm.  (O) 

7193.921 

atm.  (H.jO> 

6663.696 

Fe 

6900  199 

atm.  (O) 

7200  753 

atm.  (  H2O) 

6678.232 

Fe 

6901.113 

atm.  (O) 

7201.468 

atm.  (H.>()} 

6703.813 

p 

6904.358 

atm.  (O) 

7210.812 

at.  (H26?> 

6705-353 

? 

6905.263 

atm.  (O) 

7223.930 

5 

6717.934 

Ca 

6908.785 

atm.  (O) 

7227.765 

p 

6722.095 

p 

6909.675 

atm.  (O) 

7232.509 

7 

6726.923 

Fe 

69I3-454 

atm.  (O) 

7233-171 

p 

6750.412 

Fe 

6914.328 

atm.  (O) 

7240.972 

atrn.(H.,O) 

6752.962 

Fe 

6914.819 

Ni 

7243.904 

aun.(HaO) 

6768.044 

Ni 

6916.957 

? 

7247.461 

at.  (H,Oj? 

6772.565 

Ni 

6918.363 

atm.  (O) 

7264.851 

at.  (H2Oi? 

6787.137 

Fe 

6919.245 

atm.  (O) 

7265.833 

at.  (H2O,? 

6807.100 

Fe 

6923  557 

atm.  (O) 

7270.205 

p 

6810.519 

Fe 

6924.420 

atm.  (O) 

7273.256 

at.  (H2O)? 

6820.614 

Fe 

6928.992 

atm.  (O) 

7287.689 

at.  (H2O)? 

6828.850 

Fe 

6929.838 

atm.  (O) 

7290.714 

at.  (H20)? 

6841.591 

Fe 

6934.646 

atm.  (O) 

7300.056 

atm.(H2O) 

6843.908 

Fe 

6935-530 

atm.  (O) 

7304  475 

at.  (H2O)? 

6855.425 

Fe 

6947.781 

at.  (H20?) 

7318.  bi8 

at.  iH2Oj? 

6867.461 
6867  800 

atm.  (O) 
aim.  (O) 

6953-838 

at.  (H2O?) 
atm.? 

7321.056 
7331.206 

p 
•) 

6868.124 

atm.  (O) 

6956.700 

atm.(H20) 

7389.696 

p 

6868.393 

atm.  (O) 

6959.708 

at.  (H2O?) 

7409.554 

p 

6868.779 

atm.  (O) 

6961.518 

at.  (H2O?) 

7446.038 

•? 

6869.141 

atm.  (O)  ) 

6978.655 

p 

7462.609 

p 

6869.347 

atm.  (O)  j" 

6986.832 

atm.  (H2O) 

7495o5i 

p 

[B]  6870.186 

atm.  (O) 

6989.240 

at.  (H20?) 

7511.286 

p 

6871.179 

atm.  (O) 

6999.174 

at.  (H2O?) 

7545  921 

•? 

6871.527 

atm.  (O) 

7000.143 

? 

rA1j  7594.059 

atm  (O) 

6872.493 

atm.  (O) 

7006.  1  60 

p 

LAJ  {  7621.277 

atm.  (O) 

6873.076 

atm.  (O) 

70H.585 

p 

7623.526 

atm.  (O) 

6874.039 

atm.  (O) 

7016.279 

at.  (H2O?) 

7624  853 

aim.  (O) 

6874.884 

atm.  (O) 

7016.690 

at.  (H2O?) 

7627  232 

aim.  rO) 

6875.826 

atm.  (O) 

7023.225 

p 

7628.585 

atm.  (O) 

6876.957 

atm.  (O) 

7023.747 

? 

7659  658 

atm.  (O) 

6877.878 

atm.  (O) 

7024.988 

p 

7660.778 

Htm.  (O) 

6879.294 

atm.  (O) 

7027.199 

p 

7665  265 

atm.  (O) 

(  880.176 

atm.  (O) 

7027.726 

? 

7666.239 

atm.  (O> 

6881.970 

Cr 

7035.159 

? 

7670.993 

atm.  (O) 

6882.772 

Cr 

7038.470 

? 

7671.994 

atm.  (O> 

6883.318 

Cr 

7040.058 

? 

7699.374 

p 

6884.083 

atm.  (O) 

7090.645 

? 

7714.686 

p 

6886.008 

atm.  (O) 

7122.491 

p 

6886.987 

atm.  (O) 

7M7  942 

? 

THE   SOLAR   SPECTRUM.  1 97 

matter  of  accident  is  practically  out  of  the  question,  as  he * 
calculated  that  the  chance  of  this  being  so  is  only  I  in  a  trillion 
<TtfTnrp  oTTwioinroTro^^)-  Actually  the  chance  is  even  less,  for 
it  is  found  that,  generally,  the  brighter  an  iron  line  the  darker 
is  the  corresponding  Fraunhofer  line.  In  explanation  of  the 
above  agreement  he  suggested  that  the  light  of  the  sun  passes 
through  the  vapor  of  iron  which  absorbs  certain  of  the  rays. 
It  is  impossible  to  suppose  that  the  earth's  atmosphere 
contains  sufficient  iron  to  produce  these  absorption-lines, 
especially  as  they  undergo  no  change  when  the  sun  approaches 
the  horizon;  the  metal  must  therefore  be  present  as  vapor  in 
the  solar  atmosphere,  and  since  this  must  necessarily  be  at  an 
enormously  high  temperature,  the  presence  in  it  of  vaporized 
iron  is  not  inherently  improbable.  The  occurrence  of  one 
terrestrial  element  in  the  solar  atmosphere  having  been  thus 
demonstrated,  and  a  considerable  number  of  the  Fraunhofer 
lines  accounted  for,  Kirchhoff  sought  for  evidence  of  the 
existence  of  other  elements,  and  found  calcium,  magnesium, 
sodium,  chromium,  barium,  copper,  zinc,  and  nickel.  The 
presence  of  cobalt,  which  is  always  found  with  nickel  and  iron 
in  meteorites,  he  was  unable  to  demonstrate  positively.  The 
following  additional  metals,  which  he  investigated,  appeared 
to  be  invisible  in  the  solar  atmosphere:  gold,  silver,  mercury, 
aluminium,  tin,  lead,  antimony,  arsenic,  strontium,  lithium. 
The  researches  of  Angstrom  and  Thalen,2  separately  and  in 
conjunction,  increased  the  number  of  solar  elements,  and  led 
to  the  identification  of  about  eight  hundred  Fraunhofer  lines. 
The  following  table  shows  how  many  of  the  lines  included  in 
Angstrom's  spectrum  tables  originate  from  known  elements. 


1  Untersuchungen  iiber  das  Sonnenspectrum.     A.  B.  A.  1861. 

2  Recherches  sur  la  spectre  solaire  (Upsala,  1868). 


198  SPECTRUM  ANALYSIS. 

Element.  Number  of  lines.        Element.  Number  of  lines. 

Aluminium 2?  Iron    450 

Barium n  Magnesium 4  -(-  (3?) 

Calcium 75  Manganese 57 

Chromium 18  Nickel 33 

Cobalt 19  Sodium 9 

Copper 7  Titanium 118 

Hydrogen 4  Zinc 2? 

This  list  was  considerably  increased  by  Lockyer,1  and  light 
thrown  on  doubtful  points  by  his  method  of  long  and  short 
lines.  The  appearance  in  the  solar  spectrum  of  some,  but 
not  all,  the  reversed  coincident  lines  of  certain  elements  had 
been  noticed  by  KirchhofT  in  the  case  of  cobalt.  Lockyer 
showed  that  the  production  of  spectrum  lines  is  dependent  on 
the  temperature,  pressure,  quantity,  and  purity  of  the  vapor 
of  the  element.  The  longer  lines  require  a  lower  tempera- 
ture, and  are  most  easily  visible.  The  shorter  lines  cannot 
be  expected  to  appear  always  in  the  relatively  cool  atmosphere 
surrounding  the  sun,  consequently  their  absence  does  not 
necessarily  prove  that  a  particular  dement  is  not  present  in 
the  sun,  but  the  appearance  of  the  long  lin  s  is  sufficient  to 
establish  its  existence.  The  same  considerations  explain  why 
the  long  lines  only  are  reversed;  this  is  accomplished  by  the 
cool  atmosphere  which,  on  account  of  its  temperature,  can 
only  affect  these  and  not  the  short  ones.  In  addition  to  the 
elements  given  above,  Lockyer  has  found  the  following  in  the 
sun:  lead,  cadmium,  potassium,  cerium,  strontium,  uranium, 
vanadium,  and  probably  also  lithium,  rubidium,  caesium,  tin, 
bismuth,  and  silver.  Lockyer  has  been  led  by  his  observations 
to  certain  other  conclusions  which  have  failed  to  meet  with 
general  acceptance.  The  relative  intensity  of  the  Fraunhofer 
lines  sometimes  varies;  from  a  comparison  of  these  with 
coincident  spectrum  lines  he  considers  that  some  elements  are 
dissociated  in  the  sun;  this  gives  rise  to  certain  fundamental 
or  "  basic  lines,"  due  to  a  common  constituent  of  several 


Studies  in  spectram  analysis  (New  York  and  Lend®n,  1878). 


THE   SOLAR   SPECTRUM.  1 99 

elements.  The  incorrectness  of  this  view  has  been  established 
by  Liveing  and  Dewar,1  Fievez,"  H.  W.  Vogel,3  Kayser  and 
Runge,4  Rowland,6  and  others.  It  has  been  shown  that,  with 
few  exceptions,  the  intensity  of  the  solar  lines  is  almost  the 
same  as  that  of  the  arc  spectra  of  elements,  that  Lockyer  has 
confused  groups  of  lines  with  single  ones,  and  has  mistaken 
the  character  of  the  lines.  The  basic  lines  have  been  resolved 
by  the  use  of  higher  dispersions,  so  that  their  coincidence 
loses  its  significance;  in  the  remaining  cases  the  phenomena 
are  due  to  the  presence  of  a  common  impurity  in  the  elements 
examined.  The  number  of  elements  observed  in  the  sun  by 
Lockyer  has  also  been  modified.  Kayser  and  Runge's  work 
on  the  spectra  of  the  elements  included  an  investigation  of 
their  presence  in  the  sun;  they  showed  the  absence  of  potas- 
sium, lithium,  caesium,  and  rubidium.  The  existence  in  it  of 
carbon  and  nitrogen  was  proved  by  means  of  the  bands,  pro- 
duced by  a  compound  of  these  elements,  and  usually  termed 
the  cyanogen  bands. 

During  the  past  few  years  Rowland  8  has  thoroughly 
examined  the  Fraunhofer  lines,  and  with  the  help  of  the  con- 
cave diffraction  grating  has  also  photographed  the  spectra  of 
the  elements  in  order  to  compare  them  with  his  solar  atlas; 
the  chief  results  of  this  work  are  given  in  the  preceding  table 
of  wave-lengths.  He  finds  that  the  following  additional  ele- 
ments are  present:  lithium,  scandium,  yttrium,  zirconium, 
beryllium,  germanium,  and  erbium.  The  lists  below  repro- 
duce his  arrangement  of  elements  known  with  certainty  to  be 
present  in  the  sun;  in  the  first  they  are  arranged  according  to 
the  intensity,  in  the  second  according  to  the  number  of  the 


1  P.  R.  S.  (1881)  32.  225. 

2  Ann.  de  1'observ.  de  Bruxelles  (1882),  [2]  11. 

3  P.  M.  (1883),  [5]  15,  28 

4  A.  B.  A.  1890. 

5  Johns  Hopkins  Univ.  Circulars  (1891),  10,  42. 
•  Ibid.  (1891),  10,  41. 


SPECTRUM  ANALYSIS. 


lines.     All  elements  except  those  marked  f  occur  occasionally 
as  bright  lines  in  the  chromosphere. 


Intensity.  Number. 

1.  Calcium Iron  (at  least 

2000) 

2.  Iron -Nickel 

3.  Hydrogen Titanium 

4.  Sodium Manganese 

5.  Nickel Chromium 

6.  Manganese Cobalt 

7.  Cobalt Carbon      (at 

least  200) 

8.  Siliconf Vanadium 

9.  Aluminiumf Zirconium 

10.  Titanium Cerium 

11.  Chromium Calcium    (at 

least  75) 

12.  Strontium Neodymium 

13.  Manganese Scandium 

14.  Vanadium Lanthanum 

15.  Barium ...Yttrium 

16.  Carbonf  ? Niobium 

17.  Scandiumf Molybdenum 


Intensity.  Number. 

18.  Yttrium Palladium 

19.  Zirconiumf Magnesium  (at 

least  20) 

20.  Molybdenumf Sodium  (ii) 

21.  Lanthanum Silicon 

.22.   Niobiumf Hydrogen 

23.  Palladium! Strontium 

24.  Neodymiumf Barium 

25.  Copperf  ..- Aluminium  (4) 

26.  Zinc Cadmium 

27.  Cadmium Rhodium 

28.  Cerium Erbium 

29.  Berylliumf Zinc 

30.  Germaniumf Copper  (2) 

31.  Rhodiumf Silver 

32.  Silver Beryllium 

33-   Tin Germanium 

34.  Lead Tin 

35.  Erbium Lead  (i) 

36.  Potassiumf Potassium 


Iridium 
Osmium 


DOUBTFUL    ELEMENTS. 

Platinum  Tantalum 

Ruthenium  Thorium 


Tungsten 
Uranium 


Antimony 
Arsenic 
Bismuth 
Boron 


ABSENT    FROM    THE    SOLAR    SPECTRUM. 
Caesium  Nitrogen  (as  in  a  vacuum  tube)  Selenium 

Sulphur 


Gold 

Indium 

Mercury 


Phosphorus 

Praseodymium 

Rubidium 


Thallium 
Lithium 


ELEMENTS    NOT    YET    INVESTIGATED    BY    ROWLAND, 
Bromine  Fluorine  Holmium  Oxygen  Terbium 


Chlorine 


Gallium 


Iodine 


Tellurium  Thulium,  etc. 


The  above  results,  although  obtained  by  the  best  methods, 
are  by  no  means  final.  The  number  of  Fraunhofer  lines 
which  has  been  identified  is  large,  but  there  are  numerous 
prominent  ones  the  origin  of  which  is  unknown;  many  are 
possibly  due  to  silicon,  the  lines  of  which  in  the  visible 


THE   SOLAR   SPECTRUM.  2OI 

region  are  extremely  difficult  to  obtain,  although  those  in  the 
ultra-violet  can  be  readily  observed.  There  are  probably 
more  iron  lines  in  the  solar  spectrum  than  those  at  present 
recognized,  and  it  is  possible  that,  at  more  elevated  tempera- 
tures than  those  hitherto  attainable,  the  lines  of  all  elements 
may  increase  in  number.  The  investigation  of  many  spectra 
has  been  far  from  thorough,  and  extended  work  in  this  direc- 
tion will  probably  result  in  the  identification  of  numerous 
Fraunhofer  lines.  The  spectra  of  the  metals  of  the  rare 
earths  has  been  much  neglected;  Rowland  '  examined  several 
of  them  and  found  that  cerium,  lanthanum,  praseodymium, 
and  thorium  cannot  be  further  resolved.  Yttrium  probably 
consists  of  two  substances,  erbium  certainly  of  three  and 
possibly  of  four  elements;  one  of  these,  termed  by  Rowland 
demonium  on  account  of  the  difficulty  of  its  separation,  occurs 
in  the  sun,  and  exhibits  a  strong  line  at  about  A  =  4000.6. 
Rowland  has  also  isolated  four  other  elements  designated  by 
the  letters  h,  n,  k,  e<  three  of  them  exhibit  a  feeble  absorption- 
spectrum  in  the  visible  region,  and  a  strong  one  in  the  ultra- 
violet. 

Telluric  Lines  of  the  Solar  Spectrum.— Reference  lias 
already  been  made  to  the  telluric  or  terrestrial  Fraunhofer 
lines  produced  by  the  atmosphere  (comp.  spectrum  of  air. 
Chapter  VII).  Rowland's  table  of  wave-lengths  shows  that 
the  oxygen  and  water  vapor  of  the  atmosphere  are  the  only 
substances  which  produce  absorption  in  the  visible  region; 
nitrogen,  carbon  dioxide,  and  ozone  appear  to  exert  no 
influence.  Egoroff,2  Janssen,3  Cornu,4  and  Becker5  have  in- 
vestigated the  behavior  of  oxygen,  and  Angstrom6,  and 


1  Johns  Hopkins  Univ.  Circulars  (1894)  13,  73. 
9  C.  r.  93,  385,  788;  95,  447;  97,  555- 


%3  Ibid.  54,  1280;  56,  538;  60,  213;  63,  728.     A.  c.  p.  [4]  23,  274. 
4C.    r.    98,    169.     Journ.   de    Phys.    [2]  3,  109.     W.    A.    Beibl.   8,  305. 
A.  c.  p.  [6]  7,  5. 

6  T.  R.  S.  E.  (1890)  36,  i. 

c  C.  r.  (1866)  63,  647.     Recherches  sur  le  spectre  solaire  (Upsala,  1868). 


202  SPECTRUM  ANALYSIS. 

Janssen  l  that  of  water  vapor.  In  addition  to  known  terrestrial 
elements,  the  Fraunhofer  lines  have  led  to  the  identification  of 
others  which  have  either  not  yet  been  isolated  at  all,  or  have 
only  been  obtained  long  subsequent  to  their  spectroscopic  char- 
acterization. This  applies  to  the  Z>3-line,  produced  by  the  ele- 
ment which  Frankland  termed  helium,  and  to  the  bright  green 
line  of  the  corona  designated  by  Kirchhoff  1474^.  As  alieady 
stated,  Ramsay2  has  recently  obtained  helium  from  cleveite. 
Limits  of  the  Investigation. — It  is  somewhat  surprising 
that  so  many  terrestrial  elements,  such  as  the  non-metals,  and 
the  metals  of  high  atomic  weight,  appear  to  be  absent  from 
the  sun,  but  the  investigation  can  only  proceed  a  certain 
length.  It  has  been  already  stated  that,  in  the  ultra-violet, 
the  solar  spectrum  does  not  extend  beyond  about  3OO/*yu. 
As  the  temperature  rises  spectra  tend  to  develop  in  the 
violet;  hence,  on  account  of  the  extremely  high  temperature 
of  the  sun,  a  considerable  portion  of  its  spectrum  must  neces- 
sarily escape  observation.  Cornu  3  states  that  the  absorption 
of  the  ultra-violet  region  is  not  caused  by  the  varying  con- 
stituents of  the  atmosphere,  such  as  water  vapor  or  dust, 
but  essentially  by  nitrogen  and  oxygen.  He4  has  suggested 
a  formula  for  the  calculation  of  the  length  of  the  solar 
spectrum  absorbed  by  the  column  of  air  which  the  light 
traverses;  according  to  this,  a  thickness  of  663  metres  causes 

o 

a  diminution  of  10  A.  at  the  ultra-violet  end.  The  formula 
indicates  that  the  extreme  limit  which  can  be  observed  is 
w.-l.  =  2930,  and  it  also  shows  that  at  w.-l.  =  2120  and 
w.-l.  —  1570  total  absorption  is  caused  by  strata  of  air  10  m. 
and  o.i  m.  in  thickness,  respectively.  This  was  confirmed 
by  experiment:  the  triple  line  of  aluminium  of  w.-l.  =  1860 
was  rendered  unrecognizable  by  passage  through  a  column  of 


1  C.  r.  (i860)  63,  289,  728.     A.  c.  p.  (1871)  [4]  23,  274  ;  24,  215. 

2  C.  N.  (1893)  71,  151. 

3  C.  r.  90    940 

4  ''ibid.  88,  128=  ;  C9,  808. 


THE   SOLAR   SPECTRUM.  2O3 

air  4  m.  in  length.  A  further  obstacle  to  the  determination 
of  the  chemical  composition  of  the  sun  is  the  fact  that  its 
nucleus,  comprising  at  least  nine  tenths  of  the  whole,  is  not 
available  for  spectroscopic  investigation,  as  explained  below. 

The  Physical  Condition  of  the  Sun. — In  order  to  explain 
the  occurrence  of  the  dark  lines  in  the  solar  spectrum  Kirch- 
huff  concluded  that  the  atmosphere  of  the  sun  encloses  a 
luminous  mass  which  emits  a  continuous  spectrum  of  high 
illuminating  power.  This  inner  portion  is  either  solid  or 
liquid,  and  at  a  higher  temperature  than  the  atmosphere. 
Subsequent  investigations,  both  under  ordinary  conditions 
and  during  solar  eclipses,  have  shown  that  the  sun  is  more 
complex  than  Kirchhoff  imagined.  A  complete  treatment  of 
the  subject  is  altogether  beyond  the  scope  of  this  work,  par- 
ticularly as  opinion  is  still  much  divided;  the  majority  of 
investigators  agree  with  C.  A.  Young's  '  views,  and  it  will 
suffice  to  attempt  a  brief  sketch  of  these. 

The  nature  of  the  inner  nucleus  of  the  sun  can  only  be 
conjectured,  as  it  is  beyond  the  reach  of  observation.  Probably 
it  consists  of  gas  at  an  extremely  high  temperature,  and  under 
such  an  enormous  pressure  that  its  properties  must  resemble, 
to  some  extent,  those  of  a  viscous  substance  like  putty. 
Surrounding  the  nucleus  is  the  photosphere,  composed  of 
glowing  cloud-like  masses  of  vapor;  it  forms  the  visible  sur- 
face, and  appears  to  correspond  with  the  clouds  in  the  terres- 
trial atmosphere.  It  is  not  known  whether  it  is  separated 
from  the  nucleus  by  a  definite  surface;  externally,  it  is  sharply 
but  irregularly  defined,  being  elevated  in  some  places  into 
faculce,  and  in  others  depressed,  forming  spots.  The  reversing 
lavcr  is  situated  directly  over  the  photosphere,  and  produces 
the  Fraunhofer  lines;  its  thickness  is  only  about  1000  miles. 
The  gases  composing  the  reversing  layer  are  not  confined  ex- 
clusively to  the  surface  of  the  photosphere;  they  also  occupy 

1  The  Sun.     New  York  and  London,  1896. 

^ 
UNIVERSITY 


204  SPECTRUM  ANALYSIS. 

the  spaces  between  the  photospheric  clouds,  and  constitute 
the  atmosphere,  in  which  these  float.  Above  the  reversing 
layer  is  the  scarlet-red  chromosphere,  consisting  of  uncon- 
densed  gases  (hydrogen  and  helium);  from  this  numerous 
prominences  extend  far  beyond  the  surface  of  the  sun.  The 
exterior  portion  of  the  sun  is  termed  the  corona;  it  consists 
of  clouds  and  irregular  streams  of  light,  and  gradually  merges 
into  the  surrounding  darkness.  The  greater  portion  of  the 
mass  of  the  sun  is  within  the  photosphere,  but  the  larger  part 
of  its  volume  is  outside  it;  the  diameter  of  the  solar  atmos- 
phere is  at  least  double  that  of  the  central  portion,  and  its 
volume  consequently  seven  times  as  great  as  this. 

The  idea  that  the  NUCLEUS  of  the  sun  consists  of  gas  is 
supported  by  the  fact  that  its  atmosphere  has  a  temperature 
sufficient  to  vaporize  metals,  and  also  because  the  sun's  mean 
density  is  low.  Compared  with  that  of  the  earth  it  is  only 
0.253,  or  in  comparison  with  water  1.406;  it  would  necessarily 
be  much  greater  than  this  if  it  consisted  to  a  great  extent  of 
liquid  iron,  titanium,  magnesium,  etc.  As  the  temperature 
of  the  gaseous  mass  is  far  ;  bove  its  critical  point,  the  high 
pressure  must  cause  it  to  exceed  water  in  density,  and  there- 
fore the  gases  must  be  viscous,  and  comparable  in  properties 
with  molten  glass  or  putty. 

The  PHOTOSPHERE  is  undoubtedly  a  gaseous  envelope, 
condensed  in  places  to  cloudlike  masses  of  vapor  in  conse- 
quence of  the  heat  radiating  into  space.  Its  irregular  appear- 
ance is  due  to  these  masses,  the  solid  or  liquid  particles  of 
which  cause  its  luminosity,  and  produce  a  continuous  spec- 
trum like  the  solid  particles  in  an  ordinary  flame.  The 
spectrum  of  the  SUN-SPOTS  exhibits  a  number  of  dark  bands: 
the  dark  lines  of  calcium,  iron,  titanium,  etc.,  are  widened, 
and  some  lines,  like  those  of  hydrogen,  are  often  reversed; 
the  sodium  lines  are  also  frequently  enormously  widened, 
and  doubly  reversed,  as  shown  in  Fig.  43.  These  phenomena 
render  it  likely  that  the  increased  absorption  is  due  to  gases 


THE    SOLAR    SPECl^RUM.  2O$ 

% 

and  vapors  rushing  in  to  fill  a  space,  and  absorbing  the  light 
emitted  from  the  cavity.  In  consequence  of  the  violent 
motion  of  the  gases,  lines  are  some- 
times  displaced,  as  explained  in  the 
following  chapter. 

The  FACUL^E  show  the  H  and  K 
bands  of  calcium,  always  reversed 
by  a  thin  bright  line  running  down 
the  middle  of  each ;  and,  whilst  the  re- 
versal directly  over  a  spot  is  generally  FlG- 
"  single,"  it  is  usually  "  double  "  in  the  faculous  region  sur- 
rounding it,  i.e.,  the  bright  line  is  double.  This  makes  it 
somewhat  probable  that  the  faculae  are  not  mere  protrusions 
from  the  photosphere,  but  luminous  masses  of  calcium  vapor 
floating  in  the  solar  atmosphere,  and  possibly  identical  with 
the  prominences  themselves.  The  emission  spectrum  of  the 
REVERSING  LAYER  can  only  be  observed  during  a  total 
eclipse;  at  the  moment  when  the  sun  is  completely  obscured 
by  the  moon  the  lines  of  the  whole  spectrum  are  seen  to  flash 
out  brightly  luminous. 

Like  the  other  phenomena,  the  spectra  of  the  CHROMO- 
SPHERE and  its  PROMINENCES  were  formerly  only  visible 
during  an  eclipse;  but  in  1868  Janssen  '  and  Lockyer a  inde- 
pendently, and  almost  simultaneously,  devised  a  method  by 
which  these  portions  of  the  sun  could  be  observed  daily  in  a 
clear  atmosphere.  Zollner*  and  Huggins1  have  suggested 
similar  methods  of  procedure.  A  spectroscope  of  high  dis- 
persive power  is  employed,  and  the  slit  opened  widely;  if  not 
too  large,  the  whole  prominence  is  then  visible.  The  promi- 
nences appear  to  bear  a  certain  relationship  to  the  sun-spots 
and  faculae;  they  are  divided  into  two  classes — quiescent, 

1  C.  r.  (1868)  68,  93. 

2  P.  R.  S.  (1868)  17,  91,  104.  128. 
s  P.  A.  (1869)  138,  32. 

4  P.  R.  S.  (1868),  17,  302. 


200  SPECTRUM  ANALYSIS. 

0 

cloudlike,  or  hydrogen  and  helium  prominences,  and  erup- 
tive or  metallic  ones.  The  former  resemble  terrestrial  clouds 
in  appearance;  the  latter  are  highly  luminous,  but  the  degree 
of  luminosity  and  the  shape  change  with  extreme  rapidity. 
Their  spectra  is  very  complicated,  and,  as  shown  by  the  dis- 
placement of  the  lines,  they  often  attain  a  velocity  exceeding 
100  miles  per  second.  The  size  of  the  prominences  varies 
between  wide  limits;  the  mean  thickness  of  the  chromosphere 
is  about  7500  to  9500  km.  (5000  to  6000  miles),  therefore  no 
prominence  can  be  less  than  7000  to  9000  miles.  Secchi 
observed  2767  prominences;  of  these  1964  attained  a  height 
of  29,000  km.  (18,000  miles),  and  751  exceeded  43,000  km. 
(28,000  miles).  Young,  in  1880,  observed  a  prominence 
extending  a  distance  of  562,400  km.  (350,000  miles),  the 
longest  hitherto  noticed.  The  following  lines  form  the 
spectrum  of  the  true  chromosphere,  and  are -always  present: 

1.  7065,50  He  7.     O]  4340.66     \\y 

2.  [C]  6563.05  H<r  8.  4101.85      lift 

3.  [£>3]  5875-98  He  9.  3970.20     He 

4.  [1474  A']  5316.87     Coronal  line  10.    [H]  3968.56     Ca 

5.  [A]  4861. 50  H/J  ii.   [AT]  3933.86     Ca 

6.  [/]  4471.80  He 

There  are  numerous  additional  lines  sometimes  visible;  their 
occurrence  depends  on  the  comparative  violence  of  motion  of 
the  soJar  atmosphere.  The  principal  ones  are  the  following: 

6678.2  He  [£3]  5169.16  Fe  4491-5  Mn 

6431.1  Fe  [£4J  5167.57  Mg  4490.2  Mn 

6141.93  Ba  5018.6  Fe  4469.5  Fe 

[Z>i]  5896.2  Na  5015-7  He  4245.5  Fe 

[Z?2j  5890.2  Na  4934-25  Ba  4236.1  Fe 

5363  Fe?  4924.11  Fe  4233.8  Fe 

5284.6  Ti  ?  4922.2  He  4226.9  Ca 
5276.21  Cr?  4919.1  Fe?  4215.67  Sr 

5234.7  Mn  4900.3  Ba  4077.88  Ca 
5198-2         ?  4584.1  Fe  4026.0  He 

[<*i]  5183-79     Mg  4501.44     Ti  3889.1       H 

[£2J  5172.87     Mg 


THE   SOLAR   SPECTRUM.  2O/ 

The  Corona. — The  corona  is  visible  only  during  a  total 
eclipse,  and  much  uncertainty  prevails  as  to  its  nature.  In 
1869  Harkness,  Pickering,  and  Young  independently  observed 
the  coronal  line  1474  AT.,  of  wave-length  5316.87,  to  which 
reference  has  already  been  made.  Of  the  element  which  pro- 
duces this  line  nothing  is  at  present  known;  that  it  is  far  less 
dense  than  hydrogen  is  probable  from  the  fact  that  the  line 
remains  clear  and  sharp  during  the  most  violent  movements 
of  the  prominences.  It  was  long  believed  that  this  bright  line 
was  the  only  one  present  in  the  spectrum  of  the  corona,  but 
others,  including  those  of  hydrogen  and  calcium,  have  been 
subsequently  observed,  chiefly  by  Schuster,1  who  in  1882,  in 
Egypt,  was  able  to  detect  about  thirty.  In  addition  to  the 
bright  lines  Pickering  and  Eastman  in  1869  noticed  a  faint 
continuous  spectrum,  in  which  Janssen,  and  also  Barker 
detected  some  of  the  stronger  Fraunhofer  lines,  D,  b,  G.  It 
is  now  generally  admitted  that  the  corona  consists  of  an 
atmosphere  extending  300,000  miles,  and  of  extreme  tenuity. 
The  nature  of  the  streamers  is  still  uncertain;  some  regard 
them  as  a  sort  of  permanent  aurora,  their  position  and  direc- 
tion being  determined  by  the  sun's  magnetic  field  of  force,  as 
the  terrestrial  fields  of  force  direct  the  beams  of  the  aurora 
borealis.  Schaeberle  believes  them  to  be  due  to  light  emitted 
and  reflected  from  streams  of  matter  ejected  from  the  sun  by 
forces  acting,  in  general,  along  lines  normal  to  the  surface  of 
the  sun,  and  most  active  near  the  centre  of  each  sun-spot 
zone.  The  attempts  of  Huggins2  and  others  to  photograph 
the  corona  in  ordinary  daylight  have  not  been  successful. 

1  Abney  and  Schuster,  P.  T.  1884. 

8  P.  R.  S.  34,  409;  39,  108.     Astron.  Nachr.  104,  113.    W.  A.  Beibl.  9, 

755- 


CHAPTER    X. 

OTHER  CELESTIAL  BODIES.1  AURORA  BOREALIS.  ZO- 
DIACAL LIGHT.  LIGHTNING.  DISPLACEMENT'  OF 
THE  LINES. 

Fixed  Stars. — The  physical  condition  of  the  fixed  stars 
resembles  that  of  the  sun.  Their  continuous  spectra,  traversed 
by  rectangular  dark  lines,  shows  that  they  consist  of  an 
incandescent  mass  surrounded  by  a  glowing  atmosphere. 
Fraunhofer,  in  1817,  observed  that  the  dark  lines  differ  in  the 
spectra  of  various  stars,  and  that  they  do  not  correspond 
with  those  in  the  solar  spectrum ;  various  stellar  spectra  were 
also  correctly  characterized  by  him.  After  the  foundation  of 
an  accurate  system  of  spectrum  analysis  Secchi  and  H.  C. 
Vogel  divided  stellar  spectra  into  groups,  according  to  the 
degree  of  development  of  the  stars.  The  arrangement  is  as 
follows: 

Class  I.  Stars  at  such  high  temperatures  that  the  metallic 
vapors  in  their  atmospheres  exhibit  only  a  slight  absorptive 
power  (white  stars).  The  spectra  consist  (a)  of  strong 
hydrogen  lines  and  feeble  metallic  lines  (Sirius,  Vega,  and 
the  majority  of  white  stars);  (b)  of  single  feeble  metallic  lines 
without  the  strong  hydrogen  lines  (ft,  y,  tf,  e  Orionis);  (c)  of 
bright  hydrogen  lines,  and  the  bright  _/93-line  (<*  Lyrae,  y 
Cassiopeiae). 

Class  II.  Stars  which  resemble  the  sun,  have  an  atmos- 
phere containing  metals,  and  exhibit  a  spectrum  containing 
strong  absorption-lines.  The  spectra  show,  (a)  in  addition  to 

1  Comp.  Scheiner,  Die  Spectralanalyse  der  Gestirne  (Leipzig,  1890),  where 
a  detailed  account  is  given  of  the  subject,  with  references  to  the  literature. 

208 


OTHER    CELESTIAL   BODIES.  2OQ 

the  hydrogen  lines,  numerous  strong  metallic  lines,  especially 
in  the  yellow  and  green  (Capella,  Arcturus,  Aldebaran);  (b) 
numerous  bright  lines  together  with  dark  ones,  and  a  few 
faint  bands  (T^Coronae). 

Class  III.  Stars  at  such  a  low  temperature  that  the  sub- 
stances composing  their  atmospheres  have  combined  to  form 
chemical  compounds  which  produce  absorption-bands  (red 
stars).  The  spectra  exhibit,  (a)  in  addition  to  dark  lines, 
bands,  dark  and  sharply  defined  towards  the  violet,  whilst 
towards  the  red  they  become  irregular  (OL  Herculis,  OL  Orionis, 
ft  Pegasi).  Most  of  the  lines  are  due  to  iron,  but  it  is 
undetermined  whether  the  bands  consist  of  aggregates  of  fine 
lines,  or  of  strong  lines  extended  laterally;  (b)  dark,  very 
broad  bands,  sharply  bounded  towards  the  red,  and  gradually 
disappearing  towards  the  violet.  This  type  only  includes 
stars  of  small  mangitude,  which  is  unfortunate,  as  the  spectra 
suggests  the  possibility  of  their  atmospheres  containing  glow- 
ing carbon. 

The  Planets  and  Moon. — Since  the  planets  and  moon 
reflect  sunlight,  their  spectra  must  be  essentially  that  of  the 
sun,  modified  by  absorption-lines  or  bands  produced  by  their 
own  atmospheres.  Spectroscopic  observation  shows  that 
Mercury,  Venus,  and  Mars  have  atmospheres  similar  in  nature 
to  that  of  the  earth,  and  containing  aqueous  vapor.  The 
same  applies  to  Jupiter  and  Saturn,  but  their  spectra  exhibit 
an  additional  absorption-band;  whether  this  is  caused  by 
differences  in  temperature  and  pressure  or  by  the  presence  of 
a  new  gas  is  undetermined.  The  atmospheres  of  Uranus  and 
Neptune  also  differ  materially  from  that  of  the  earth,  and 
contain  an  additional  constituent  in  large  quantity. 

The  spectrum  of  the  moon  is  in  every  way  identical  with 
that  of  the  sun,  showing  that  it  has  no  atmosphere,  or  only 
one  of  extreme  tenuity.  The  satellites  of  Jupiter  exhibit  the 
same  spectra  as  that  of  the  planet  itself,  and  appear  to  have 
identical  atmospheres. 


210  SPECTRUM  ANALYSIS. 

Comets. — The  first  spectroscopic  observation  of  a  comet 
was  made  by  Donati  in  1864;  he  found  that  the  spectrum 
consisted  of  three  bright  bands  superposed  on  a  continuous 
spectrum,  and  that,  in  part  at  least,  the  comet  was  self- 
luminous.  Four  years  later  Huggins  stated  that  the  bright 
bands  were  identical  with  those  obtained  by  passing  electric 
sparks  through  ethylene.  Subsequent  accurate  measurements 
made  by  H.  C.  Vogel,  and  Hasselberg  showed  that  this  is 
not  the  case,  although  the  comets  undoubtedly  contain  carbon 
in  considerable  quantity.  A  spectrum  very  similar  to  that  of 
a  comet  is  obtained  by  passing  a  continuous  electric  discharge 
through  a  mixture  of  a  h\drocarbon  and  carbon  monoxide. 
The  comet  I  of  1882  was  observed  by  H.  C.  Vogel  to  contain 
sodium;  this  was  confirmed  by  Duner  and  Bredichin,  whilst 
Copeland  and  J.  G.  Lohse  noticed  iron  lines  in  comet  II  of 
1882,  which  passed  within  a  few  thousand  miles  of  the  sun. 
Huggins,  in  1881,  observed  that  the  continuous  spectrum 
exhibits  the  Fraunhofer  lines,  proving  that  a  portion  at  least 
of  its  light  is  reflected  sunlight.  Photometric  and  spectro- 
scopic observations  of  a  sudden  outburst  of  light  in  the  case 
of  comet  I  of  1884  showed  that  a  part  of  the  continuous 
spectrum  is  due  to  the  comet's  own  luminosity.  Hasselberg 
has  suggested  that  this  is  probably  caused  by  electrical  forces, 
and  observations  of  other  kinds  have  rendered  it  very  probable 
that  comets  are  the  seats  of  electrical  activity. 

Meteors  and  Shooting  Stars  do  not  lend  themselves  to 
spectroscopic  observation  on  account  of  the  short  period 
during  which  they  are  visible.  They  exhibit  a  continuous 
spectrum,  caused  by  the  incandescence  of  the  solid  constit- 
uents, but  in  addition  to  this  only  the  sodium  line  has  been 
observed  with  certainty.  The  meteorites  which  fall  on  to  the 
earth  can  all  be  analyzed  by  the  ordinary  chemical  methods, 
so  that  their  spectroscopic  investigation  is  not  of  much  im- 
portance. 

Nebulae. — The  spectroscopic   investigation  of  the  nebulae 


OTHER    CELESTIAL   BODIES.  211 

is  of  considerable  interest  in  connection  with  the  Kant- 
Laplace  hypothesis  of  the  origin  of  the  solar  system.  Formerly 
they  were  classified  as  divisible  nebulae,  which  could  be 
resolved  into  clusters  of  stars,  and  indivisible  or  true  nebulae; 
but  the  latter  were  regarded  as  being  capable  of  resolution  if 
sufficiently  powerful  telescopes  were  available.  The  first 
spectroscopic  observations  of  nebulae  were  made  by  Huggins 
in  1864;  he  noticed  the  existence  of  bright  lines,  showing  the 
presence  of  luminous  gases.  The  faintness  of  the  light  renders 
the  investigation  a  matter  of  difficulty;  with  medium  instru- 
ments three  or  four  lines  only  are  usually  visible.  The  wave- 
lengths are  about  5004,  4957,  4861,  4341.  By  means  of 
photographic  processes  about  forty  additional  lines  may  be 
detected.  The  presence  of  hydrogen  is  known  with  certainty, 
and  that  of  helium  is  probable,  but  the  origin  of  the  majority 
of  the  lines  is  unknown.  Many  of  the  nebulae  exhibit  a  faint 
continuous  spectrum  in  addition  to  the  bright  lines;  its  maxi- 
mum is  in  the  green,  instead  of  the  yellow.  Vogel  states 
that  it  shows  no  sign  of  discontinuity,  but  Copeland  and 
Huggins  consider  that  it  appears  to  be  resolved  into  lines. 
If  this  view  is  correct,  the  nebulous  clusters  of  stars  are  masses 
of  glowing  gas,  and  are  to  be  regarded  as  stellar  systems,  the 
individuals  of  which  are  gaseous. 

Aurora  Borealis. — This  phenomenon  is  the  result  of  elec- 
tric discharges  in  highly  rarefied  air,  and  has  been  a  frequent 
subject  of  spectroscopic  observation.  The  spectrum  exhibits 
a  number  of  very  faint  lines,  together  with  a  characteristic 
bright  green  one  of  wave-length  =  5571,  which  has  been 
termed  the  aurora  line.  Its  origin  is  not  known,  but  H.  C. 
Vogel,  Zollner,  and  Hasselberg  agree  in  regarding  the  remain- 
ing portion  of  the  spectrum  as  a  modification  of  that  of  air. 

The  spectrum  of  the  ZODIACAL  LIGHT  is  a  reflected  solar 
spectrum;  the  faintness  of  the  light  necessitates  the  use  of  a 
wide  slit,  so  that  the  Fraunhofer  lines  are  unrecognizable. 

The  spectrum  of  LIGHTNING  has  been  examined  by  many, 


212  SPECTRUM  ANALYSIS. 

including  Kundt,  John  Herschel,  Laborde,  H.  C.  Vogel, 
Joule,  Procter,  Young,  and  Schuster.  The  majority  have 
detected  the  line  spectrum  of  nitrogen,  frequently  in  combina- 
tion with  a  continuous  spectrum,  and  occasionally  with  a 
band-spectrum  of  unknown  origin.  Schuster  states  that  this 
last  bears  a  very  close  resemblance  to  the  spectrum,  at  the 
cathode,  of  a  vacuum  tube  containing  oxygen  mixed  with  a 
small  proportion  of  carbon  monoxide. 

DISPLACEMENT    OF    THE    LINES. 

The  spectroscope  has  rendered  important  help  to  astrono- 
mers in  elucidating  the  relative  velocity  of  bodies  in  the  line 
of  collimation.  In  the  sections  on  sun-spots  and  prominences 
it  was  mentioned  that  their  extremely  rapid  motion  produced 
a  displacement  of  the  spectrum  lines.  The  explanation  of 
this  phenomenon  is  obtained  from  Doppler's1  principle,  first 
propounded  in  1841,  according  to  which  the  color  of  the  light 
received  on  to  the  retina,  or  the  pitch  of  a  note  changes  if  the 
source  of  light  or  sound  approaches  or  recedes  from  the 
observer  at  a  speed  not  too  small  in  comparison  to  that  of 
light  or  sound  respectively.  If  the  source  of  light  or  sound 
approaches  the  observer  more  waves  will  be  received  in  a 
given  time  than  if  it  were  stationary,  whilst  if  it  is  receding 
the  number  of  waves  will  be  less.  V  The  color  or  wave-length 
of  a  ray  from  an  object  approaching  will  therefore  be  diverted 
towards  the  violet,  but  will  approximate  to  the  red  if  the 
object  is  receding.  yThe  alteration,  to  a  stationary  observer, 
according  to  whether  the  light  approaches  or  recedes,  is  given 

by  the  expression  X,  =  A  1 1  ±  -],  where  A  =  the  wave-length 

of  the  ray,  A,  =  that  produced  by  the  motion,  v  being  the 
velocity  of  light,  and  a  that  of  the  luminous  body. 


1  Ueber  das  farbige   Licht  der  Doppelsterne  und  anderer  Gestirne  des 
Himmels.     Abhandl.  K.  Bohmischen  Ges.  d.  Wissensch.  (1841-2)  [5]  2,  465. 


OTHER    CELESTIAL   BODIES. 


213 


44  shows  the  displacement  of  the  /Mine  in  the  spectrum  of  a 
sun-spot.  Huggins,  in  1864,  first  employed  the  displacement 
of  the  lines  to  determine  the  velocity  of  Sirius  in  the  line  of 


FIG.  44 

collimation.      He  observed  that  the  wave-length  of  the 

had   increased  O.iOQyU//;   the  velocity  of  light  —  297,100  km. 

per  second,   and  the  wave-length  of   the  /<-line  =  486.5^. 

297100  X  0.109 
Consequently  the  expression  Q^; ~  66.6   shows 

that,  at  the  time  of  the  observation,  Sirius  and  the  earth  were 
receding  at  the  rate  of  66.6  km.  per  second ;  but  the  earth  was 
itself  moving  from  Sirius  at  the  rate  of  19.3  km.,  so  that  the 
speed  of  the  latter  is  reduced  to  47.3  km.  Subsequent 
observations,  with  improved  instruments,  led  Huggins  to- 
modify  this  to  29 — 35  km.  per  second.  Similar  investiga- 
tions of  the  stars  and  nebulae  have  been  made  by  H.  C. 
Vogel,  Seabroke,  and  the  Greenwich  astronomers.  Lockyer 
and  Young  have  employed  the  method  for  the  determination 
of  the  velocity  of  portions  of  the  solar  atmosphere,  so  far  as» 
they  move  in  the  line  of  collimation.  The  speed  with  which- 
changes  take  place  is  enormous,  and  often  resembles  a  violent 
cyclone;  the  rising  and  sinking  masses  of  gas  in  the  spots, 
attain  a  velocity  of  30  to  50  miles  per  second,  whilst  that  of 
the  prominences  is  frequently  150  km.  (100  miles)  per  second, 
and  occasionally  twice  as  gre.at. 


INDEX  OF  AUTHORS. 


Abney,  7,  62,  151,  184,  188,  207 
Adeney,  8,  97,  101,  104,  108,  121,  131, 

135,    142,    143,    145,   148,    151,    154, 

160,  165,  166,  167,  172 
Allen,  108 
Ames,  20,  45,  88,   89,    108,    128,    164, 

o  I72 
Angstrom,  4,  6,  62,   76,  92,    104,   109, 

no,  114,    117,   118,    128,    135,    144, 
146,    148,   149,  151,    153,    154,    164, 
188,  197,  201 
Attfield,  107,  in,  162 

B 

Bahr,  124,   125 

Bailey,  124 

Balmer,  8,  80,    129 

Becker,  151,  201 

Becquerel,  E.,62,  63,  96,  104,  143,  157, 
162 

Becquerel,  H.,  63,  109,  124 

Beilstein,  155 

Bell,  92,  108,  152 

Bernthsen,  179 

Berthelot,  99,  128 

Boisbaudran,  Lecoq  de,  Q,  58,  65,  80, 
86,  87,  88,  96,  97,  102,  105,  108,  10^, 
ii?,  117,  118,  121,  122,  124,  125, 
126,  130,  131,  135,  142,  143,  I44» 
145,  146,  151,  152,  154,  155,  156, 
T57»  J58,  161,  162,  163,  166,  167, 
172 

Bolton,  170 


Brauner,  127 

Brewster,  2,  118,  144,  151,  152,  186 

Briihl,  150 

Brunner,  136 

Bunsen,  5,  20,  58,  65,  79,  95,  102,  108, 
116,  122,  124,  125,  141,  142,  143, 
157,  158,  162,  163,  166,  171 

C 

Cappel.  96 

Capron,  8,  130 

Cauchy,  37 

Cazin,  8 

Chappuis,  151 

Christiansen,  16 

Christie,  20,  31 

Christofle,  155 

Ciamician,  89,  101,  103,  105,  115,  117, 

132,  156,  160,  164,  166 
Clayden,  131 
Cleve,  127,  141,  158 
Clifton,  5 
Collie,  127 
Cornu,  7,  59,  6r,  77,  81,  96,   103,   108. 

109,    119,    128,    135,    143,    144,    146, 

151,    162,    166,   168,    172,    188,   201, 

202 

Crookes,  98,  103,  124,  166,  171 
Currie,  63 

D 

Daniell,  105.  132 
Delachanal,  57 
Delafontaine,  122 
y,  8 

215 


i6 


INDEX  OF  AUTHORS. 


Desains,  61,  63 

Deslandres,  59,  69,  81,  86,  114,  115, 
126,  130,  148,  149,  154 

Dewar,  8,  54,  77,  81,  96,  97,  102,  104, 
108,  109,  no,  in,  114,  117,  119, 
121,  125,  126,  130,  131,  135,  141, 
142,  143,  144,  145,  146,  150,  154, 
157.  J58,  160,  161,  162,  166,  167", 
168,  172,  199 

Diacon,  53,  122,  142,  157,  162 

Dibbits,  8,  in,  114,  152 

Dieterici,  9 

Ditte,  89,  101,  117,  164,  165 

Doppler,  212 

Dorn,  99 

Dove,  149 

Draper,  9,  62,  115,  198 

Dupr6,  58 

E 

Ebert,  52,  68 

Eder,   53,   68,  98,  99,   105,    109,    no, 

ii2,  145,  152,  160,  163 
Egoroff,  151,  201 
Eisig,  154 
Emsmann,  31 
Erdmann,  99 
Erhard,  118 
Etard,  118,  119 
Ewan,  121,  130,  136,   177 


Ferry,  62 

Festing,  184,  188 

Fievez,  in,  143,  151,  188,  199 

Foucault,  4,  76 

Frankland,  73 

Franz,  61 

Fraser,  153 

Friedlander,  100 

Fraunhofer,  4,  17,  186 

Fuchs,  31 

G 

Gange,  9 

Galitzin,  73 

Gernez,  132,  152,  160,  164,  165 


Gladstone,  64,  122,  144,  145,  151,  177, 

186 

Glan,  40,  122 
Glazebrook,  20 
Goldstein,  151 
Goske,  179 
Gouy,  52,   155 
Grace,  130  . 
Gramont,    A.    de,    9,    157,    160,    162,. 

164 

Grandeau,  9 
Grebe,  180 
Greiner,  136 
Grubb,  25 
Griinvvald,  89 

H 

Hagenbach,   170 
Haitinger,  124 
Hale,  127 
Hartley,  8,  57,  89,  97,   101,   103,  104, 

105,    108,    112,    121,    131,    135,    136, 

142,    143,   144,    145,   148,    150,    154, 

155,    160,   165,    166,    167,    172,    181, 

182,  183 
Hasselberg,   59,  67,  97,  105,  117,  119, 

129,    132,    146,   148,    149,    152,    154^ 

164,  168,  171,  175 
Hautefeuille,  89,    105,    112,    151,    160, 

173 

Helmholtz,  H.  v.,  16,  60 
Helmholtz,  R.  v.,  62 
Hennesay,  151 
Herschel,  Alex.,  31 
Herschel,  A.  S.,  114,  115 
Herschel,  John,  2 
Herschel,  William,  61 
Heycock,  131 
Higgs,  9 
Hittorf,  71,  77,  101,  105,  m,  115,  117, 

128,    132,    141,    148,   151,    153,    155, 

160,  163 

Hofmann,  152,  155 
Holden,  156 
Hiifner,  40 
Huggins,  6,  9,   10,  97,   101,   102,   104, 

109,    in,    117,    118,    124,    126,    127,. 


INDEX   OF  AUTHORS. 


217 


128,  130,  135,  142,  144,  145,  151, 
153.  J55,  156,  157,  161,  162,  165, 
166,  167,  172,  205,  207 

Humphreys,  128 

Huntington,  101,  182,  183 

Hutchins,  154,  156 


Janssen,  28,    130,   151,   154,   2OI,  2O2, 

205 

Jewell,  Lewis  E.,  154 
Johnson,  108 
Julius,  62,  69,  87,  96 

K 

Kahlbaum,  2 

Kayser,  8,  9,  49,  54,  67,  69,  81,  87,  88, 
89,  96,  97,  99,  101,  102,  104,  107,  108, 
109,  in,  114,  i2t,  126,  127,  129,  131, 
135,  141,  143,  145,  157,  158,  161,  162, 
1 66,  167,  172,  199 

Kelvin,  10 

Kempf,  7,  92,  189 

Kessler,  31 

Ketteler,  142 

Kirchhoff,  2,  5,  6,  20,  76,  95,  96,  97, 
101,  102,  103,  108,  109,  116,  117,  118, 
121,  122,  126,  134,  135,  141,  142, 143, 
145,  146,  151,  155,  156,  157,  158,  161, 
162,  167,  172,  188,  197 

Klinkerfues,  9 

Knoblauch,  O.,  79,  177 

Kobb,  125 

v.  Kovesligethy,  9,  87 

Kohn,  136 

v.  Konkoly,  9 

Kopp,  2 

v.  Kostanecki,  179 

Kruss,  G.,  9,  38,  64,  65,  118,  122,  124, 
126,  144,  159,  179 

Kriiss,  H.,  9,  64,  118,  122,  144 

Kundt,  16,  78 

Kuppelwieser,  136 

Kurlbaum,  92 


Lamansky,  61 

Landauer,  64,  177 

Langley,  7,  60,  62,  63,  151,  189 

Lapraik,  118,  130 

Lassel,  10 

Lewis,  62 

v.  Lichtenfels,  136 

Liebermann,  C.,  179 

Lielegg,  9,  112,  136 

Lippich,  73,  124 

Listing,  95 

Littrow,  25 

Liveing,  8,  54,  77,  81,  96,  97,  102,  104, 
108,  109,  in,  114,  117,  119,  121,  125, 
126,  130,  131,  135,  141,  142,  143,  144, 
145,  146,  150,  154,  157,  158,  160,  161, 
162,  166,  167,  168,  172,  199 

Lockyer,  7,  9,  69,  73,  77,  97,  98,  iory 
1 02,  103,  108,  109,  no,  in,  115,  116, 

117,  119,  122,  127,  128,   134,   135,  141, 

144,  146,  153,  155,  156, 157,  161,  162, 

164,  166,  167,  168,  169,  170,  171,  172, 

173,  198,  205 
Lommel,  10,  63,  189 
Lorscheid,  9 

M 

MacMunn,  9 
Magnanini,  152,  177 
Mascart,  20,   104,   108,   109,   135,  i6r, 

162,  167,  172,  188 
Masson,  4 
Melloni,  61 
Melville,  Thomas,  2 
Mermet,  57 

Miller,  W.  A.,  3,  7,  105,  132,  146,  166, 
Mitscherlich,  5,  53,  102,  104,  109,  115, 

122,  125,  132,  141,  152,  160,  163 
Monckhoven,  59 
Morghen,  132 
Morren,  in,  115,  117,  152 
Morton,  170 
Moser,  105,  152 
Mouton,  61 
Miiller,   7,  92,  118,  136,  142,  162,  188, 

189 


218 


INDEX   OF  A  UTHORS. 


Miiller,  J.,  61 
Miiller  C-Pouillet),  10 
Mulder,  155,  160,  164 

N 

Neovius,  154 
Newall,  99 
Newton,  15 
Nilson,  124,  159 

O 

Oeconomides,  S.,  179 
Oeffinger,  170 
Orstnan,  119 
Ostwald,  44,  177 


Paalzow,  154 

Palmieri,  127 

Parker,  Spear,  136 

Paschen,  62,  127,  128,  154 

Pearce,  145 

Peirce,  92 

Pfaundler,  10 

Piazzi-Smyth,   59,   III,   114,   130,  148, 

151,  154,  188 
Pickering,  20,  129 
Pliicker,  5,  58,  71,  101,  105,  in,  114, 

115, 117,  128,  132,  141,  145,  148,  151, 

153.  155,  160,  163 
Pringsheim,  77 
Proctor,  9 


Ramsay,  98,  127,  202 

Rayleigh,  16,  20,  98 

Reich,  131 

Reusch,  20 

Reynolds,  80,  118,  124 

Richard,  128 

Richards,  100,  106,  117,  132,  149 

Richter,  131 

Rilliet,  182 

Roberts,  98,  141.  166,  167 

Roscoe,  5,  9.  72,  79,  105,  136 


Rosen berger,  2 

Rowland,  7,  20,  45,  92,  103,  105,  126, 
153,  154,  156,  157,  158,  160,  166,  171, 

189,    190,   199,  2OI 

Rubens,  60,  62 

Riihlmann,  142 

Runge,  8,  20,  54,  67,  69,  81,  87,  89,  96, 
97,  lor,  102,  104,  107,  108,  109,  in, 
114,  121,  126,  127,  128,  131,  135,  141, 
142,  143,  145, 154,  157,  158,  161,  162, 
i(>6,  167,  172,  199 

Russell,  119,  130 

Rutherfurd,  26,  157,  162 

Rydberg,  8,  69,  84,  109,  128,  162 


Sabatier,  118,  122 

Sabine,  121 

Salet,  10,  53,  58^  59,  105,  112,  117,  125, 

128,  132,  148,  154,  155,  157,  159,  160, 

164,  165,  167 
Sarasin,  130 
Scheiner,  10,  44,  208 
Schellen,  10 
Schonn,  130 
Schottlander,  124 
Schumann,  60,  61 
Schiitze,  180 
Schuster,  8,  69,  72,  80,  124,  148,  152, 

153,  164,  207 
Seabroke,  129 
Secchi,  10,  135,  151 
Seguin,  125,  155,  163 
Sellmeier,  16 
Sieben,  16 
Siemens,  W.  v.,  77 
Snow,  62 
Sorby,  40 

Soret,  60,  80,  124,  130.  158,  182 
Spring,  182 
Stenger,  78,  177 
Stewart,  Balfour,  76 
Stokes,  2,  6r,  76,  170 
Stoney,  80,  87,  118 
Swan,  3,  in,  162 


INDEX  OF  AUTHORS. 


2I9 


Tait,  10 

Talbot,  Fox,  2,  114 

Tatnall,  103,  105,  126,  153,  154,  156, 
157,  158 

Thal6n,  7,  10,  86,  92,  96,  97,  101,  102, 
103,  104,  105,  108,  109,  no,  in,  114, 
115, 116,  117,  118,  121,  122,  124,  126, 
131, 132,  135, 141,  142,  143,  144, 145, 
146,  148,  149,  150,  153,  154,  155,  156, 
157,  158,  159,  161,  162,  165,  166,  167, 
168,  169,  170,  171,  172,  197 

Thiele,  132 

Thollon,  20,  25,  114,  151,  188 

Thorpe,  105 

Travers,  127 

Troost,  89,  105,  112,  160,  173 

Trowbridge,    100,   106,   117,  121,  132, 

149.  *54 
Tuckerman,  10 
Tunner,  136 
Tyndall,  10 


Valenta,  53,  98,  99,  105.  109,  no,  145, 

160,  163 

Vierordt,  10,  39 
Vogel,  E.,  179 
Vogel,  H.  C.,  129,  148,  149 
Vogel,  H.  W.,  10,  30,  44,  58,  64,  78, 

117,  118,  119,  128,  132, 134,  135,136, 


142,    144,    145,  146,   154,   167,  170, 

175,  180,  199 

W 

Wagner,  177 
Walter,  44 

Watts,  10,  93,  in,  114,  115,  136,  145 
Wedding,  136 
Welsbach,  Auer  v.,  124 
Wesendonck,  112,  114,  115 
Wheatstone,  4 

Wiedemann,  E.,  55,  68,  69,  77 
Witt,  O.  N.,  181 
Willigen,    van   der,    5,    in,   117,    148, 

149 

Winkelmann,  10,  69,  81,  88 
Wollaston,  3,  16,  no,  137,  186 
Wolf,  53,  142,  157,  162 
Wolff,  C.H.,  119,  121 
Wright,  10 
Wiillner,    69,    71,    73,    112,    114,    115, 

129,  132,  148,  154 


Young,  10,  203 


Zeeman,  75 
Zimniermann,  170 
Zollner,  73,  205 


INDEX  OF  SUBJECTS. 


A 

PAGES 

A-line..    ii,  18,  66 

Abnormal  dispersion 15 

Absorption  and  emission  of  light,  interrelationship 6,  76,  197 

fluorescence 79 

phosphorescence . .     79 

bands,  displacement  produced  by  increasing  atomic  weight  132,  181 

substitution  in  organic   com- 
pounds    180,181 

coefficient 79 

of  light  by  gases  and  liquids 175 

in  the  infra-red «. 184 

ultra-violet 182,  202 

visible  region  of  the  spectrum 179 

mechanism ....      77 

-spectra i,  63,  76,  174 

and  color,  interrelationship 180 

molecular  structure,  interrelationship 78,  178 

influence  of  concentration  of  a  solution 177 

increasing  atomic  weight 132,  181 

optical  density 79 

position  of  substituting  groups 180 

solvent 78 

state  of  aggregation 77 

substituting  radicles 179,  182 

temperature 77 

observation  of 63,  1 74 

photometric 39 

table  of : 176 

thickness  of  layer  of  active  substance 64,  79 

Aggregation,  influence  on  absorption-spectrum 78 

Air,  absorption-spectrum ........    151 

221 


222  INDEX   OF  SUBJECTS. 


Air,  line-spectrum 149,  ii>i 

lines  in  metallic  spectra 57,  149 

liquid,  spectrum  of  electric  discharge  in 1 50 

refractive  index 13,  67 

Albumins,  ultra-violet  absorption-spectra 184 

Albuminoids,  ultra-violet  absorption-spectra 184 

Alcohol,  refractive  index 13 

Alcohols  CMH2«+i.OH  ultra-violet  absorption-spectra 182,  183 

Aldebaran  spectrum 209 

Alizarin  absorption-spectrum 1 76 

Alumina  arc  (band)  spectrum 97 

Aluminium 96 

arc-spectrum 96 

spark-spectrum 96 

Amines   15° 

Ammonia  infra-red  absorption-spectrum   184 

line  (flame)  spectrum 149,  152 

Angle,  refractive 13 

Angstrom's  unit 12 

Aniline-blue  absorption-spectrum 176 

Antimony 97 

absorption-spectrum. 98 

arc-spectrum 98 

spark-spectrum 98 

Arc-spectra,  production  of 54 

Arcturus  spectrum 209 

Argand  burner 63 

Argon 98 

blue  (spark)  spectrum 100 

red  (spark)  spectrum 100 

white  (spark)  spectrum 101 

Arsenic 101 

arc-spectrum 102 

spark-spectrum 102 

Astigmatism  of  concave  grating 48 

Atlas,  Angstrom's 6,  188,  189 

Cornu's 7,  188- 

Rowland's 7,  189 

Atmosphere,  terrestrial,  absorptive  action 151,  1 86,  201,  202 

Atomic  and  luminiferous  vibrations,  interrelationship 70 

vibrations  of  molecules 70,  73 

weight  and  spectra,  interrelationship 87,  88,  91 

calculation  of,  from  homologous  lines 88 

Aurora  borealis  spectrum 211 

Azo-group,  influence  on  organic  dyes 180,  1.81 


INDEX    OF  SUBJECTS  22$ 

B 

PAGES 

£-\me 1 8,  66 

/Mine 65,  206,  207 

^2-,  ^s-,  ^4- line 66,  206 

Band-spectra 69 

formula  for  calculation  of  (Deslandres) Si,  86 

regularities  in  construction  of 86 

Barium 102 

arc-spectrum 1 03 

spark-spectrum 103 

Barium  bromide  flame-spectrum 103 

chloride  flame-spectrum 103 

iodide  flame-spectrum 103 

oxide  flame-spectrum .    103 

Basic  lines 198 

Benzene  and  derivatives  ultra-violet  absorption-spectra 182 

Beryllium 103 

arc-spectrum 103 

fluorescent  spectrum 103 

spark-spectrum 103 

Bessemer  converter  flame-spectrum 1 36 

Bismuth 104 

arc-spectrum 104 

spark-spectrum 104 

oxide  flame-spectrum 104 

salts  flame-spectrum , . . . .    104 

Blood-pigments  absorption-spectra > 176 

stains,  identification 175 

Bolometer  (Langley's) 62,  197 

Boric  acid  flame  (band)  spectrum 105 

Boron 104 

arc-spectrum 105 

spark-spectrum 105 

Broadening  of  spectrum  lines 73,  75 

Bromine 105 

absorption-spectrum 106 

spark  (line)  spectrum 106 

a-Bromonaphthalene  coefficient  of  refraction ,  . .  .      13 

use 44 

Burner,  Auer's 44,  63 

Bunsen's 51,  54 

Terquem's 51,  53 


224  INDEX   OF  SUBJECTS. 


C 

PAGFS 

C-line 18,  66,  206 

Cadmium 107 

arc-spectrum 108 

spark-spectrum  108 

bromide  flame-spectrum 108 

chloride  flame-spectrum 108 

Caesium 108 

arc-spectrum 108 

flame-spectrum 108 

spark-spectrum 1 08 

Calcium 109 

arc-spectrum 109 

flame-spectrum 109 

spark-spectrum 109 

bromide  flame-spectrum no 

chloride  flame-spectrum no 

fluoride  flame-spectrum no 

oxide  flame-spectrum no 

Calculation  of  the  position  of  spectrum-lines  (Kayser  and  Runge) 82 

(Rydberg) 85 

Capella  spectrum .  209 

Carbohydrates  ultra-violet  absorption-spectrum   184 

Carbon no 

band  (flame,  arc)  spectrum in,  113 

line  (spark)  spectrum 113 

bands  in  metallic  spectra 112 

presence  in  comets 210 

stars    209 

bisulphide  refractive  index 13 

use  in  hollow  prisms 27 

monoxide  band  (spark)  spectrum 114 

toxicological  detection 1 76 

haemoglobin 176 

X-Cassiopae  spectrum  208 

Cathochromic  groups , 1 8 1 

Cerium 116,  201 

spark-spectrum 116 

Channelled  spectra 69,   71 

Chlorine , 116 

absorption-spectrum 117 

spark-spectrum 117 

Chlorophyll  absorption-spectrum 1 76 

Chromium 117 


UNIVERSITY 


INDEX  OF  SUBJECTS.  225 

PAUES  ' 

Chromium  arc-spectrum 118- 

spark-spectrurn 117 

compounds  absorption-spectrum 118,  176- 

spectro-analytical  determination 1 18 

Chromophors , 181 

Chromosphere 206 

Chrysoldins  absorption-spectra 179 

Classification  of  colors  (Listing) 95, 

Cinnamate  ethylic  refraction  coefficient 13 

use  in  hollow  prisms 28 

Cobalt 1 18 

arc-spectrum 119 

spark-spectrum 119 

chloride  and  ammonium  thiocyanate 119 

glass  absorption-spectrum 119 

salts  absorption-spectrum   119,  176 

spectro-analytical  determination 119 

Coefficient  of  extinction   79 

Coincidence  method  (Rowland) 49 

Collimator 22,  48 

tube 21 

Color  and  absorption-spectrum,  interrelationship 1 80 

of  salt    solutions,   conformation  with    Arrhenius'    dissociation    hy- 
pothesis   177 

Colors,  classification  of  (Listing) 95 

complementary 180 

combined  produce  whiteness 14,  180- 

explanation 1 80 

wave-lengths   95 

Comets  spectra 210 

self-luminosity 210 

Comparison  photographs 48 

spectrum   22 

Complementary  colors     180- 

Concave  grating  (Rowland) 7,  34,  45,  47.  63,  189 

spectrograph  (Rowland) 45 

spectroscope  (Rowland) 33 

Continuous  spectra i,  69 ' 

Copper 121 

arc-spectrum .^ 122 

spark-spectrum 122 

chloride  flame-spectrum 122 

salts  absorption-spectrum 121,  176 

spectro-analytical  determination 121 

Cooling  of  flames  for  production  of  spectra 51 


226  INDEX  OF  SUBJECTS. 

PAGES 

Corona 207 

Coronal  lines 202,  206,  207 

7-Coronae  spectrum ...      209 

Correction  table  (Watts)  for  Angstrom's  scale  94 

Crown-glass  refraction  coefficient 13 

Cyanogen  band-spectrum 112,  114 

D 

ZMines 4,  n,  16,  18,  76,  207 

ZVline  wave-length n,  18,  49,  66,  190,  206 

ZVline  wave-length 66,  206 

Z>3-line 126,202,   206 

Delicacy  of  spectrum  reactions . . '. 95 

Demonium  spectrum 201 

Deviation,  minimum 14 

Diagrams  of  spectra 68 

Didymium. 122 

spark-spectrum 123 

chloride  absorption-spectrum 123,  124 

earths  absorption-spectrum 123 

nitrate  absorption-spectrum , 1 24 

Diffraction  grating,  see  Grating. 

discovery  by  Fraunhofer 17 

of  light 17 

Discontinuous  spectra I 

Dispersion,  abnormal 15 

curve 66 

formula  (Cauchy) 37 

increase  ol 23 

of  light 14 

Displacement  of  lines 212 

Dissociation,  electrolytic 79,  132 

hypothetical,  of  elements  in  the  sun.  . . ., 198 

Doppler's  principle , 212 

Double  lines 82 

Dyes,  organic,  properties  dependent  on  the  presence  of  specific  groups  in 

the  molecule 180 

theory  of  (Schiitze) i&o 

E 

^-line.... 18.66 

Elements  present  in  the  sun 197 

Emission  and  absorption  of  light,  interrelationship 76 

of  light i 

spectra 69 


INDEX   OF  SUBJECTS.  22$ 

PAGES 

Eosin  absorption-spectrum 176,  180 

Erbium 124,  201 

spark-spectrum 124 

chloride  absorption-spectrum 125 

Esters,  see  Ethereal  salts. 

Ether,  luminiferous.. n 

ultra-violet  absorption-spectra 183 

Ethereal  salts,  ultra-violet  absorption-spectra 182 

Eihylic  cinnamate  refractive  index  13 

Extinction  coefficient , 79 

Eyepiece  (Gauss) 37 

F 

T^-line ...'. 66,  206,  212 

Faculae 203,  205 

Fatty  acids  ultra-violet  absorption-spectrum 182 

Fixed  stars  spectrum 208 

Flame-spectra,  apparatus  for  producing 52 

Flint-glass  refraction  coefficient. . . 13 

Fluorescein  absorption-spectrum. 176 

Fluorescence  and  absorption 79 

Fluorine 125 

flame-spectrum   125 

spark-spectrum 125 

Fluor-spar  refraction-coefficient 13 

Formula,  Balmer's 81,  82 

Deslandres' ,  ..   81,  86 

Fraunhofer  lines 76,  151,  186,  189,  191,  200 

Fuchsin  (magenta)  absorption-spectrum 176 

G 

<7-line *..... 18,  66,  207 

Gallium .  . 125 

arc-spectrum . . 125 

spark-spectrum 125 

spectro-analytical  calculation  of  atomic  weight 89 

Gases,  spectroscopic  investigation  of 58 

Gauss'  eyepiece 37 

Geissler  tubes , , ^ 58 

filling  of 58 

Germanium. .  . . 125 

arc-spectrum. ...... , 126 

spark-spectrum 126 

spectro-analytical  calculation  of  atomic  weight. 88 


228  INDEX   OF  SUBJECTS. 

PAGES 

Glass,  contamination  of  spectra  by 26 

Schultz's 39 

gratings 17 

Gold 126 

arc-spectrum 126 

spark-spectrum 126 

Graphic  representation  of  spectra 68 

Grating 16 

constant 32 

holder 47 

plane  and  concave  (Rowland) 17,  33,  63 

reflection 17 

separatory  power 19 

spectra, 'production  of 31 

spectroscope   31,  45. 

transparent 17 

H 

J/-line 18,  66,  206 

Haematin  absorption-spectrum 176 

Half-prisms  (Christie) 31 

Harmonic  relationship  of  spectrum  lines 8,  80 

series  (Liveingand  Dewar) 8,  81 

Heating  effect  of  various  regions  of  the  solar  spectrum 61 

Helium 126 

spark-spectrum 127 

ft- Hercules  spectrum    209 

H  istory  of  spectrum  analysis 2 

Hollow  prisms  for  the  observation  of  absorption-spectra 64 

Homologous  lines  of  different  elements 87 

Hydrogen I2& 

compound  line-spectrum 130 

elementary  line-spectrum 130 

infra-red  lineal  absorption-spectrum 184 

flame 51 

lines,  formula  for  calculating  (Balmer) 81,  82,  129 

Hypsochromic  groups 181 

I 

Incandescent  burner  ( Auer's) 44,  63 

Indigo  absorption-spectrum  1 76 

Indium , 131 

arc-spectrum 131 

flame-spectrum 131 

spark-spectrum 131 


INDEX  OF  SUBJECTS.  22$ 

PACKS 

Induction-spark 55 

Influence  machine 55 

Infra-red  (ultra-red)  rays 61 

method  of  observation   61 

designation  of  lines  in 189 

Instruments  for  spectrum  analysis 20 

Intensity  numbers 95 

scales. ... 95 

of  spectrum-lines 95 

Interference,  law  of 18 

Interpolation-curve  construction 66 

Iodine. 132 

absorption-spectrum . .  r 133 

spark-spectrum 133 

compounds  absorption-spectrum 133 

Ions 177 

Iridium 134 

arc-spectrum  1 34 

ammonium  chloride  absorption-spectrum 134 

Iron 135 

arc-spectrum 137 

spark-spectrum 135 

salts  absorption-spectrum 135,  176 

Isomeric  compounds  absorption-spectra 183 

J 

Jena  glass  refractive  index 13 

Jupiter  spectrum 209 

Jupiter's  satellites  spectrum , 209 

K 

AMine ' n,  66,  206 

Kirchhoff's  law 6,  197 

Kundt's  rule 78,  178 

L 

Lamp  (Bartel's) 51 

Lanthanum 141,  201 

spark-spectrum 141 

Law  of  exchanges  (Kirchhoff) 6,  76,  197 

objections  to , 77 

Layer,  reversing. . .    198,  203,  205 

Lead 141 

arc-spectrum 142 


230  INDEX   OF  SUBJECTS. 

PAGES 

Lead  spark-spectrum 142 

oxide  band-spectrum . ; 141 

Leyden  jar 55 

Light,  anomalous  dispersion 15 

diffraction 17 

dispersion 14 

homogeneous : 15 

reflection 12 

refraction 12 

theory  of  (Huygens) n 

velocity n,  212 

vibrations,  relation  to  atomic  vibrations 70 

white,  composition  (Newton) 15 

Lightning  spectrum 211 

Line  1474  K  (coronal  line) 202.  206,  207 

displacement 212 

of  collimation,  motion  of  luminous  bodies  in 212 

pairs 82,  91 

spectra , . . . .     69 

triplets 85,  91 

Lines,  basic  (suppositive) i  q8 

Fraunhofer 76,  151,  186,  189,  191,  200 

origin 6,   77 

homologous • 87 

long  and  short  (Lockyer) 73,   198 

.of  a  spectrum,  formula  for  the  calculation  of  (Kayser  and  Runge). . .     82 

(Rydberg) 84 

an  element,  interrelationship 80 

spontaneous  reversal 72 

widening  by  increase  of  pressure 72 

in  magnetic  current. 75 

Lithium 142 

arc-spectrum , j 42 

flame-spectrum 142 

spark-spectrum 142 

Luminescence  (Wiedemann) 77 

Luminiferous  ether n 

Luminous  paint  (Balmain's) 63 

a-Lyrae  spectrum 208 

M 

Magenta  (fuchsin)  absorption-spectrum 176 

Magnesium 142 

arc-spectrum 143. 


INDEX  OF  SUBJECTS. 

PAGES 

Magnesium  flame-spectrum 143, 

spark-spectrum 143, 

hydride  band-spectrum 144: 

oxide  band-spectrum 144. 

Magnetic  current,  influence  on  spectrum-lines 76 

Malachite  green  absorption-spectrum 176 

Manganese 144 

arc-spectrum 145, 

spark-spectrum 145; 

oxide  spark-spectrum   145 

salts  absorption-spectrum 144,  176 

spectro-colorimetric  determination 144^ 

Mars  spectrum 2091 

Measuring  appliances,  spectroscopic 65,  67 

Mercury 145. 

arc-spectrum 145 

spark-spectrum 145,. 

(planet)  spectrum 2og» 

Metal  gratings 31 

Meteors  and  shooting  stars , 210 

Methyl  violet  absorption-spectrum 176 

Micromillimetre  (/n/j) 12 

Microspectroscope 40 

Miniature  spectroscope 29 

Minimum  of  brightness,  determination  by  Kriiss*  method 64,  174. 

deviation *. .  14 

automatic  adjustment  in  position  of 24 

Molecular  structure  and  absorption-spectrum  relationship 178,  179,  182 

of  matter,  investigation  of 69 

Molecules,  atomic  movement  of . 70 

of  gases 69,  70 

liquids 69,  70 

solids 69,  70 

Molybdenum   146 

spark-spectrum 146 

Monckhoven's  tubes   59 

a-Monobromonaphthalene  in  hollow  prisms   44 

Moon  spectrum 209 

Motion  of  luminous  bodies  in  the  line  of  collimation , 213, 

N 

Nebulae  spectrum 210* 

Nebulous  series  (Rydberg) 285 

Neodymium 1 22. 


232  INDEX   OF  SUBJECTS. 

I'AGF.S 

Neptune  spectrum 209 

Nickel 146 

arc-spectrum   147 

spark-spectrum 147 

salts  absorption-spectrum 146,  176 

Niobium 147 

Nitric  acid  infra-red  absorption-spectrum 184 

Nitrogen 148 

band-spectrum  (-f-  pole) 151 

(-  pole) 151 

line-spectrum 1 50 

spectrum  of  electric  discharge  in  liquid 1 50 

Nitrous  anhydride  (NO  -f-  NO2)  absorption-spectrum 150,  152 

Normal  lines,  Rowland's  table  of 191 

O 

Orientation  of  spectra 113,  135 

a-Orionis  spectrum 209 

/S-,  Y't  $-,  6-Orionis  spectra 208 

Oscillation  frequency 67 

Osmium 153 

arc-spectrum 153 

spark-spectrum 153 

Oxygen 153 

band-spectrum , .  154 

compound  line-spectrum 154 

elementary  line-spectrum 154 

inorganic  radicles  infra-red  absorption-spectrum 1 84 

liquid,  spectrum  of  electric  discharge  in 150 

Oxyhaemoglobin  absorption-spectrum 1 76 

Oxyhydrogen  flame , 51 

P 

Pairs 82,  91 

Palladium 1 54 

arc-spectrum 155 

spark-spectrum 155 

/f-Pegasi  spectrum 209 

Phosphorus 155 

band  (flame)  spectrum 155 

line  (spark)  spectrum 155 

Phosphorescence 79 

Phosphorescent  action  of  infra-red  rays 63 

Photographic  plates  (Abney) 62,  188 

(Schumann) 61 


INDEX  OF  SUBfECTS.  233 

PACKS 

Photographic  plates  without  gelatine  for  ultra-violet  rays 6r 

Photography,  spectroscopic  use  of 44,  47,  62,  180 

Photosphere 203,  204 

Planets  spectrum 209 

Platinum 156 

arc-spectrum 156 

spark-spectrum « 156 

salts  absorption-spectrum 156 

Plucker's  tubes 58 

Pocket  spectroscope 29 

Potassium 1 56 

arc-spectrum 157 

flame-spectrum 1 56 

spark-spectrum 157 

Potsdam  system 7 

Praseodymium  spectrum 201 

nitrate  absorption-spectrum 124 

Pressure,  influence  on  spectrum  lines 72 

Principal  series  (Kayser  and  Runge) 83 

(Rydberg) 85 

Prism  material,  coefficients  of  refraction t 13 

spectroscopes  with  angular  vision 20 

direct  vision 28 

Prisms 13 

compound  (Amici) 28 

hollow 24 

refracting  angle  14 

edge 14 

faces 13 

Rutherfurd's 26,  44 

separatory  power 16 

totally  reflecting 25 

Prominences,  solar 42,  205 

eruptive 206 

quiescent 205 

velocity 206,  213 

s-Puppis  spectrum t 129 

Purpurin  absorption-spectrum 176 

0 

Quantitative  spectrum  analysis 39,  118,  119,  lai,  144 

Quartz  lenses  and  prisms 61 

refractive  coefficient , 13 

Quinine  sulphate  for  observation  of  ultra-violet  rays 60 

Qu  incline  red  absorption -spectrum 176 


234  INDEX  OF  SUBJECTS. 


R 

PAGES 

Rain-band 129 

Rare  earths  spectra 201 

ultra-violet  absorption-spectra 122 

Rays,  infra-red -    61 

ultra-violet 60 

Red  sta  rs •  •   209 

Reduction  of  Angstrom's  to  Rowland's  scale 94 

scale-measurements  to  wave-lengths    66 

Reflection  of  light 12 

prism 22 

Refraction  coefficient 13 

index 13 

of  light. 12 

Regularities  in  the  construction  of  spectra 8,  80 

Relationship  between  the  lines  of  an  element 8,  80 

spectra  of  different  elements 8,87 

Representation  of  spectra 68 

Reversal  of  spectrum  lines 72,  203 

Reversing  layer  of  solar  atmosphere 198,  203,  205 

Rhodium 157 

arc-spectrum 157 

Rubidium , 158 

arc-spectrum 15$ 

flame-spectrum 15& 

spark-spectrum 158 

Rule,  Kundt's 78,  178 

Ruthenium    158 

arc- spectrum , 158 


S 

Safranine  absorption-spectrum 176 

Salet's  tubes 59 

Salt  solutions,  color  of,  and  Arrhenius'  dissociation  theory 177 

Salts  with  a  common  colored  basic  or  acidic  radicle 177 

Samarium !  58 

spark-spectrum 159. 

nitrate  absorption-spectrum 159 

Saturn  spectrum 209 

Srale,  Angstrom's u)  92 

Bunsen's. 65,  66 

Rowland's 66,  92 


INDEX   OF  SUBJECTS.  235 

PAGES 

Scale  divisions,  conversion  into  wave-lengths 66 

Scales 65,  67,  92 

inequality  of 65 

Scandium 159 

spark-spectrum 159 

Schultz's  glasses ' 39 

Selenium.  ...      , 159 

band-spectrum 160 

spark-spectrum 160 

compounds  absorption-spectrum 160 

Separatory  power  of  a  grating 19 

prism 19 

Series,  harmonic 81 

of  lines,  principal,  nebulous,  sharp  (Rydberg) 85 

of  an  element 81,  84 

Silicious  flint-glass  refractive  index 13 

Silicon 160 

spark-spectrum 160 

fluoride  spark  (flame)  spectrum 125 

Silver 161 

arc-spectrum 161 

spark-spectrum 161 

Sirius  motion  in  line  of  collimation 213 

spectrum 208 

Slit  construction 22,  48 

introduction 16 

tube  (collimator) 22,  48 

wedge-shaped 44 

Snell's  law 13 

Sodium 161 

arc-spectrum   162 

flame-spectrum 161 

spark-spectrum 162 

(D)  line 4,  n,  16,  18,  76,  207 

Solar  atlas,  Angstrom's 6,  188,  189 

Cornu's  (ultra-violet) 7,  188 

Rowland's 7,  189 

atmosphere,  presence  of  terrestrial  substances  in 197 

velocity 206,  2 1 2 

faculae   203,  205 

nucleus 203,  204 

prominences 42,  205 

spectroscopes 41 

spectrum 6 

absorption  of  ultra-violet  region 202 


236  INDEX   OF  SUBJECTS. 

PAGES 

Solar  spectrum  Cornu's  atlas  of  ultra-violet  region 7,  188 

Kirchhoff's  drawings 188 

normal,  Angstrom's  atlas 6,  188,   189 

Rowland's  photographic  atlas 7,  189 

photography  of  infra-red  region 62,  1 88 

telluric  lines. ...    151,   186,  201 

Solutions,  spectroscopic  examination 64 

Spark  gap,  introduction  into  circuit 55 

spectra  3 

production 55 

Spectra,  diffraction,  merits  of 19 

grouping  in  agreement  with  periodic  system 82 

influence  of  magnetic  current 75 

pressure 72 

temperature , 72 

of  different  elements,  interrelationship. 8,  87,  89 

electric  spark,  first  observation 3 

first  order  (Pliicker  and  Hittorf) 71 

second  order    Pliicker  and  Hittorf) 71 

recording  of  (Bunsen) 68 

in  accordance  with  number  of  vibrations 90 

refraction,  merits  .. 19 

relationship  to  atomic  weights 83,  91 

Spectrographs 43 

Spectrometers 35 

Spectrophotometer 39 

Spectroscopes  angular  vision 20 

direct  vision 28 

grating 31 

Spectroscopic  charts 188 

instruments  35 

Spectrum  i,  92 

absorption  ...  174 

Spectrum  analysis,  applications I,  8,  40,  92,  1 36 

foundation  by  Bunsen  and  Kirchhoff 2,  5 

general  bibliography S 

history 2 

physical  basis 1 1 

province i 

quantitative 39,  118,  119,  121,  144 

band 69 

change  of,  dependent  on  alteration  in  atomic  vibration 70 

channelled  space 69.  71 

constancy  in  the  same  order : 71 

continuous i ,  69 


INDEX   OF  SUBJECTS.  2$? 

PAGBS 

Spectrum  definition I 

discontinuous i 

invisible,  observation Go 

line 69 

lines,  widening 72,  75,  205 

of  an  element  different  from  that  of  its  compounds 5,  71 

electric  discharge  in  highly  rarefied  gases  (Plucker) 5 

orientation 6,  67,  135,  186 

pure 16 

reactions,  delicacy 95 

Spontaneous  reversal  of  spectrum-lines 72 

Stars  spectrum 208 

red 209 

shooting  and  meteors 210 

white 208 

Stellar  spectrometers 43 

spectroscopes 41 

Strontium 162 

arc-spectrum 163 

spark-spectrum 163 

chloride  flame-spectrum 163 

compounds  flame-spectrum     162 

oxide  flame-spectrum 163 

Sub-series,  first  and  second  (Kayser  and  Runge)  82 

Substituting  groups  in  organic  compounds 171; 

influence  on  position  of  absorption-bands 179 

Sulphur. 163 

band-spectrum 164 

line-spectrum 164 

Sun  chemical  composition 190 

light  as  an  illuminant 63 

physical  condition v 203 

spots 203,  204 

Survey,  spectroscopic,  of  the  sky 43 

Swan's  carbon-spectrum no 

Symmetrical  path  of  rays  through  a  prism 14 

T 

Fable  for  reduction  of  wave-lengths  to  Rowland's  scale 94 

Tantalum 164. 

Telluric  lines  in  solar  spectrum 151,  186,  201 

Tellurium 1 64 

band-spectrum 165 

spark-spectrum 1 03 


238  INDEX   OF  SUBJECTS. 


Tellurium  bromide  absorption-spectrum 165 

chloride  absorption-spectrum 165 

Temperature  influence  on  absorption-spectrum   77 

spectrum  lines 72 

of  Bunsen  flame 54 

electric  arc   54 

spark 55 

Terrestrial  lines  of  solar  spectrum,  see  Telluric  lines. 

Thallium 165 

arc-spectrum 166 

flame-spectrum 1 66 

spark-spectrum 166 

Thorium 166,  201 

spark-spectrum 166 

Thulium 167 

spark-spectrum 167 

oxide  band-spectrum 167 

salts  absorption-spectrum 167 

Tin 167 

arc-spectrum 168 

spark-spectrum 168 

oxide  band-spectrum. 167 

Titanium 168 

arc-spectrum 168 

spark-spectrum 168 

Triplets 85,  89,  91 

Tubes,  Geissler's 58 

Monckhoven's 59 

Salet's 59 

Tungsten 169 

spark-spectrum 1 70 

U 

Ultra-red  rays,  see  Infra-red  rays. 

Ultra-violet  rays 60 

method  of  observation 6O 

Unit,  Angstrom's 12 

Universal  spectroscope  (Kriiss) 38 

Uranium 170 

spark-spectrum 1 70 

glass,  use  for  observation  of  ultra-violet  rays 60 

Uranium  salts  absorption-spectrum ,  .. , .   170,  176 

Uranus  spectrum « 209 


INDEX  OF  SUBJECTS.  239 

V 

PAGES 

Vacuum-tubes,  filling 'of 58 

Vanadium 171 

arc-spectrum 171 

spark-spectrum 171 

Vapor,  production  of  glowing , 51 

Vega  spectrum 208 

Velocity  of  light 213 

Venus  spectrum 209 

W 

Water  absorption-spectrum , 130 

in  infra-red 184 

refractive  index « 13 

vapor  absorption-spectrum 129 

Wave-length u,  188 

change  in,  by  the  approach  or  recession  of  the  source  of  light.  212 

determinations  of  the  /Mines 92 

of  the  colors 95 

table  of  the  Fraunhofer  lines  (Rowland).    191 

unit II,  92 

use  in  orientation  of  spectra 190 

White  stars 208 

Widening  of  spectrum  lines 72,  75,  205 

Y 

Ytterbium 171 

spark-spectrum 171 

Yttrium 171,  201 

phosphorescent  spectrum 171,  172 

spark-spectrum 172 

Z 

Zinc 172 

arc-spectrum    172 

spark-spectrum 172 

Zirconium.. . .    172 

light  (Linnemann's) 63 

spark-spectrum... . , 173 

Zodiacal-light  spectrum 211 


SHORT-TITLE    CATALOGUE 

OF  THE 

PUBLICATIONS 

OF 

JOHN   WILEY   &    SONS, 

NEW    YORK, 

LONDON:    CHAPMAN    &    HALL,   LIMITED. 
ARRANGED  UNDER  SUBJECTS. 


Descriptive  circulars  sent  on  application. 

Books  marked  with  an  asterisk  are  sold  at  net  prices  only. 

All  books  are  bound  in  cloth  unless  otherwise  stated. 


AGRICULTURE. 

CATTLE  FEEDING— DAIRY  PRACTICE — DISEASES  OF  ANIMALS — 
GARDENING,  ETC. 

Armsby's  Manual  of  Cattle  Feeding, 12mo,  $1  75 

Downing's  Fruit  and  Fruit  Trees Svo,  5'  00 

Grotenfelt's  The  Principles  of  Modern  Dairy  Practice.     (Woll.) 

12mo,  2  00 

Kemp's  Landscape  Gardening 12mo,  2  50 

Lloyd's  Science  of  Agriculture Svo,  4  00 

Loudon's Gardening  for  Ladies.     (Downing.) 12mo,  1  50 

Steel's  Treatise  on  the  Diseases  of  the  Dog Svo,  3  50 

"      Treatise  on  the  Diseases  of  the  Ox Svo,  600 

Stockbridge's  Rocks  and  Soils Svo,  2  50 

Woll's  Handbook  for  Farmers  and  Dairymen 12mo,  1  50 

ARCHITECTURE. 

BUILDING — CARPENTRY —  STAIRS — VENTILATION,  ETC. 

Berg's  Buildings  and  Structures  of  American  Railroads 4to,  7  50 

Birkmire's  American  Theatres — Planning  and  Construction.  Svo,  3  00 

Architectural  Iron  and  Steel Svo,  3  50 

f   •",<>     Compound 'Riveted  Girders Svo,  2  00 

Skeleton  Construction  in  Buildings Svo,  3  00 

Planning  and  Construction  of  High  Office  Buildings. 
1 


Carpenter's  Heating  and  Ventilating  of  Buildings 8vo,  $3  00 

Downing,  Cottages Svo,  2  50 

"        Hints  to  Architects ,Svo,  2  00 

Freitag's  Architectural  Engineering Svo,  2  50 

Gerhard's  Sanitary  House  Inspection 16mo,  1  00 

Theatre  Fires  and  Panics 12mo,  1  50 

Hatfield's  American  House  Carpenter Svo,  5  00 

Holly's  Carpenter  and  Joiner ISmo,  75 

Kidder's  Architect  and  Builder's  Pocket-book Morocco  flap,  4  00 

Merrill's  Stones  for  Building  and  Decoration Svo,  5  00 

Monckton's  Stair  Building — Wood,  Iron,  and  Stone 4to,  4  00 

Wait's  Engineering  and  Architectural  Jurisprudence Svo,  6  00 

Sheep,  6  50 

Worcester's  Small  Hospitals — Establishment  and  Maintenance, 
including  Atkinson's  Suggestions  for  Hospital  Archi- 
tecture  12mo,  125 

World's  Columbian  Exposition  of  1893 4to,  2  50 

ARMY,  NAVY,  Etc. 
MILITARY  ENGINEERING — ORDNANCE — PORT  CHARGES,  ETC. 

Bourne's  Screw  Propellers .4to,  5  00 

Bruff  s  Ordnance  and  Gunnery Svo,  6  00 

Buckuill's  Submarine  Mines  and  Torpedoes Svo,  4  00 

Chase's  Screw  Propellers Svo,  3  00 

Cooke's  Naval  Ordnance Svo,  12  50 

Cronkhite's  Gunnery  for  Non-coin.  Officers ISmo,  morocco,  2  00 

De  Brack's  Cavalry  Outpost  Duties.     (Carr.). . .  .ISmo,  morocco,  2  00 

Dietz's  Soldier's  First  Aid 12mo,  morocco,  1  25 

*  Dredge's  Modern  French  Artillefy 4to,  half  morocco,  20  00 

Record   of   the   Transportation   Exhibits    Building, 

World's  Columbian  Exposition  of  1893.. 4to,  half  morocco,  10  00 

Dyer's  Light  Artillery 12mo,  3  00 

Hoff's  Naval  Tactics Svo,  1  50 

Hunter's  Port  Charges Svo,  half  morocco,  13  00 

Ingalls's  Ballistic  Tables Svo,  1  50 

Handbook  of  Problems  in  Direct  Fire Svo,  4  00 

Mahau's  Advanced  Guard ISmo,  1  50 

"      Permanent  Fortifications.  (Mercur.).8vo,  half  morocco,  7  50 

Mercur's  Attack  of  Fortified  Places 12mo,  2  00 

2 


Mercur's  Elements  of  the  Art  of  War 8vo,  $4  00 

Metcalfe's  Ordnance  and  Gunnery 12uio,  with  Atlas,  5  00 

Murray's  A  Manual  for  Courts-Martial 18mo,  morocco,  1  50 

"        Infantry  Drill  Regulations  adapted  to  the  Springfield 

Rifle,  Caliber  .45 18mo,  paper,  10 

Phelps's  Practical  Marine  Surveying 8vo,  2  50 

Powell's  Army  Officer's  Examiner 12mo,  4  00 

Reed's  Signal  Service 50 

Sharpe's  Subsisting  Armies 18mo,  morocco,  1  50 

Todcl  and  Whall's  Practical  Seamanship 8vo,  7  50 

Very's  Navies  of  the  World 8vo,  half  morocco,  3  50 

Wheeler's  Siege  Operations 8vo,  2  00 

Wiuthrop's  Abridgment  of  Military  Law 12mo,  2  50 

Woodhull's  Notes  on  Military  Hygiene 12mo,  morocco,  2  50 

Young's  Simple  Elements  of  Navigation..  12mo,  morocco  flaps,  2  50 

ASSAYING. 

SMELTING — ORE  DRESSING— ALLOYS,  ETC. 

Fletcher's  Quant.  Assaying  with  the  Blowpipe..  12mo,  morocco,  1  50 

Furnian's  Practical  Assaying 8vo,  3  00 

Kuuhardt's  Ore  Dressing 8vo,  1  50 

*  Mitchell's  Practical  Assaying.     (Crookes.) 8vo,  10  00 

O'Driscoll's  Treatment  of  Gold  Ores 8vo,  2  CO 

Ricketts  and  Miller's  Notes  on  Assaying 8vo,  3  00 

Thurston's  Alloys,  Brasses,  and  Bronzes, . , 8vo,  2  50 

Wilson's  Cyanide  Processes l"2rno,  1  50 

The  Chlorination  Process 12mo,  150 

ASTRONOMY. 

PRACTICAL,  THEORETICAL,  AND  DESCRIPTIVE. 

Craig's  Azimuth 4to,  3  50 

Doolittle's  Practical  Astronomy 8vo,  4  00 

Gore's  Elements  of  Geodesy 8vo,  2  50 

Michie  and  Harlow's  Practical  Astronomy 8vo,  3  00 

White's  Theoretical  and  Descriptive  Astronomy 12mo,  2  00 

BOTANY. 

GARDENING  FOR  LADIES,  ETC. 

Baldwin's  Orchids  of  New  England 8vo,  1  50 

Loudon's  Gardening  for  Ladies.     (Downing.) 12mo,  1  50 

3 


MacCord's  Kinematics ... 8vo,  $5  00 

"          Mechanical  Drawing 8vo,  400 

Mahan's  Industrial  Drawing.    (Thompson.) 2  vols.,  8vo,  3  50 

Reed's  Topographical  Drawing.     (II.  A.) 4to,  5  00 

Smith's  Topographical  Drawing.     (Macmillan.) 8vo,  2  50 

Warren's  Descriptive  Geometry 2  vols.,  8vo,  3  50 

"        Drafting  Instruments . . '.  ...12mo,  1  25 

' '        Free-hand  Drawing    12mo,  1  00 

"        Higher  Linear  Perspective 8vo,  3  50 

"        Linear  Perspective 12mo,  100 

"        Machine  Construction. 2  vols.,  8vo,  7  50 

"        Plane  Problems , 12mo,  125 

"        Primary  Geometry .  ...12mo,  75 

"        Problems  and  Theorems 8vo,  2  50 

"         Projection  Drawing . . . 12mo,  1  50 

"        Shades  and  Shadows 8vo,  3  00 

"        Stereotomy— Stone  Cutting 8vo,  2  50 

Whelpley's  Letter  Engraving ...  12mo,  2  00 

ELECTRICITY  AND  MAGNETISM. 

ILLUMINATION — BATTERIES — PHYSICS. 

Anthony  and  Brackett's  Text-book  of  Physics  (Magie).    ...8vo,  400 

Barker's  Deep-sea  Soundings. 8vo,  2  00 

Benjamin's  Voltaic  Cell 8vo,  3  00 

History  of  Electricity 8vo  3  00 

Cosmic  Law  of  Thermal  Repulsion ;..... 18mo,  75 

Crehore  and  Squier's  Experiments  with  a  New  Polarizing  Photo- 
Chronograph 8vo,  3  00 

*  Dredge's  Electric  Illuminations.  . .  .2  vols. ,  4to,  half  morocco,  25  00 

Vol.  II...' 4to,  7  50 

Gilbert's  De  magnete.     (Mottelay.) 8vo,  2  50 

Holman's  Precision  of  Measurements 8vo,  2  00 

Michie's  Wave  Motion  Relating  to  Sound  and  Light Svo,  4  00 

Morgan's  The  Theory  of  Solutions  and  its  Results 12mo,  1  00 

Niaudet's  Electric  Batteries.     (Fishback.) . .  12mo,  2  50 

Reagan's  Steam  and  Electrical  Locomotives 12mo  2  00 

Thtirston's  Stationary  Steam  Engines  for  Electric  Lighting  Pur- 
poses     12mo,  1  50 

Tillman's  Heat 8vo,  1  50 


ENGINEERING. 

CIVIL — MECHANICAL — SANITAKY,  ETC. 

(See  also  BRIDGES,  p.  4 ;  HYDRAULICS,  p.  8 ;  MATERIALS  OF  EN- 
GINEERING, p.  9  ;  MECHANICS  AND  MACHINERY,  p.  11  ;  STEAM  ENGINES 
AND  BOILERS,  p.  14.) 

Baker's  Masonry  Construction 8vo,  $5  00 

Baker's  Surveying  Instruments 12mo,  3  00 

Black's  U.  S.  Public  Works 4to,  5  00 

Brook's  Street  Railway  Location , 12mo,  morocco,  1  50 

Butts's  Engineer's  Field-book 12mo,  morocco,  2  50 

Byrne's  Highway  Construction 8vo,  7  50 

Carpenter's  Experimental  Engineering. 8vo,  6  00 

Church's  Mechanics  of  Engineering — Solids  and  Fluids 8vo,  6  00 

"        Notes  and  Examples  in  Mechanics 8vo,  2  00 

Crandall's  Earthwork  Tables 8vo,  1  50 

Crandall's  The  Transition  Curve 12mo,  morocco,  1  50 

*  Dredge's  Penn.  Railroad  Construction,  etc.  .  .  Folio,  half  mor.,  20  00 

*  Drinker's  Tunnelling 4to,  half  morocco,  25  00 

Eissler's  Explosives — Nitroglycerine  and  Dynamite 8vo,  4  00 

Gerhard's  Sanitary  House  Inspection .16mo,  1  00 

Godwin's  Railroad  Engineer's  Field-book.  12mo,  pocket-bk.  form,  2  50 

Gore's  Elements  of  Geodesy 8vo,  2  50 

Howard's  Transition  Curve  Field-book 12mo,  morocco  flap,  1  50 

Howe's  Retaining  Walls  (New  Edition.) , 12mo,  1  25 

Hudson's  Excavation  Tables.    Vol.  II 8vo,  1  00 

Button's  Mechanical  Engineering  of  Power  Plants 8vo,  5  00 

Johnson's  Materials  of  Construction 8vo,  6  00 

Johnson's  Stadia  Reduction  Diagram.  .Sheet,  22£  X  28£  inches,  50 

Theory  and  Practice  of  Surveying 8vo,  4  00 

Kent's  Mechanical  Engineer's  Pocket-book 12mo,  morocco,  5  00 

Kiersted's  Sewage  Disposal 12mo,  1  25 

Kirkwood's  Lead  Pipe  for  Service  Pipe 8vo,  1  50 

Mahan's  Civil  Engineering.      (Wood.) 8vo,  5  00  • 

Merriman  and  Brook's  Handbook  for  Surveyors. . .  .12mo,  mor.,  2  00 

Merriman's  Geodetic  Surveying 8vo,  2  00 

"          Retaining  Walls  and  Masonry  Dams 8vo,  2  00 

Mosely's  Mechanical  Engineering.     (Mahan.) 8vo,  5  00 

Nagle's  Manual  for  Railroad  Engineers 12mo,  morocco,  3  00 


Pattern's  Civil  Engineering 8vo,  $7  50 

"       Foundations 8vo,  500 

Rockwell's  Roads  and  Pavements  in  France 12mo,  1  25 

Ruffiier's  Non-tidal  Rivers  8vo,  1  25 

Searles's  Field  Engineering 12mo,  morocco  flaps,  3  00 

"       Railroad  Spiral 12mo,  morocco  flaps;  1  50 

Siebert  and  Biggin's  Modern  Stone  Cutting  and  Masonry. .  .8vo,  1  50 

Smith's  Cable  Tramways 4to,  2  50 

"       Wire  Manufacture  and  Uses 4to,  3  00 

Spaldiug's  Roads  and  Pavements 12mo,  2  00 

"         Hydraulic  Cement 12mo,  2  00 

Thurstou's  Materials  of  Construction, 8vo,  5  00 

*  Trautwiue's  Civil  Engineer's  Pocket-book.  ..12mo,  uior.  flaps,  5  00 

*  "           Cross-section Sheet,  25 

*  "           Excavations  and  Embankments 8vo,  2  00 

*  "           Laying  Out  Curves 12mo,  morocco,  2  50 

Waddell's  De  Pontibus  (A  Pocket-book  for  Bridge  Engineers.) 

Wait's  Engineering  and  Architectural  Jurisprudence 8vo,  6  00 

Sheep,  6  50 

Warren's  Stereotomy — Stone  Cutting 8vo,  2  50 

Webb's  Engineering  Instruments 12mo,  morocco,  1  00 

Wegmann's  Construction  of  Masonry  Dams 4to,  5  00 

Wellington's  Location  of  Railways 8vo,  5  00 

Wheeler's  Civil  Engineering 8vo,  4  00 

Wolff's  Windmill  as  a  Prime  Mover 8vo,  3  00 

HYDRAULICS. 
WATER-WHEELS — WINDMILLS — SERVICE  PIPE — DRAINAGE,  ETC. 

(See  also  ENGINEERING,  p.  6.) 
Bazin's  Experiments  upon  the  Contraction  of  the  Liquid  Vein 

(Trautwine) 8vo,  2  00 

Bovey's  Treatise  on  Hydraulics 8vo,  4  00 

Coffin's  Graphical  Solution  of  Hydraulic  Problems 12mo,  2  50 

Ferrel's  Treatise  on  the  Winds,  Cyclones,  and  Tornadoes. .  .8vo,  4  00 

Fuerte's  Water  and  Public  Health 12mo,  1  50 

Ganguillet  &  Kutter's Flow  of  Water.  (Heriug&Trautwiue.).8vo,  4  00 

Hazeu's  Filtration  of  Public  Water  Supply 8vo,  2  00 

Herschel's  115  Experiments 8vo,  2  00 

Kiersted's  Sewage  Disposal 12mo,  1  25 


Kirk  wood's  Lead  Pipe  for  Service  Pipe 8vo,  $  1  50 

Masou's  Water  Supply 8vo,  5  00 

Merrimaii's  Treatise  oil  Hydraulics. .  - , 8vo,  4  00 

Nichols's  Water  Supply  (Chemical  and  Sauitary) 8vo,  2  50 

Ruffner's  Improvement  for  Non-tidal  Rivers 8vo,  1  25 

Wegmaun's  Water  Supply  of  the  City  of  New  York 4to,  10  00 

Weisbach's  Hydraulics.     (Du  Bois.) 8vo,  5  00 

Wilsou's  Irrigation  Engineering • ...  .8vo,  4  00 

Wolff's  Windmill  as  a  Prime  Mover 8vo,  3  00 

Wood's  Theory  of  Turbines 8vo,  2  50 

MANUFACTURES. 

ANILINE— BOILERS— EXPLOSIVES— IRON— SUGAR — WATCHES  — 
WOOLLENS,  ETC. 

Allen's  Tables  for  Iron  Analysis 8vo,  3  00 

Beaumont's  Woollen  and  Worsted  Manufacture 12ino,  1  50 

Bolland's  Encyclopaedia  of  Founding  Terms 12mo,  3  00 

The  Iron  Founder 12mo,  250 

"                               "        Supplement 12mo,  250 

Booth's  Clock  and  Watch  Maker's  Manual 12mo,  2  00 

Bouvier's  Handbook  on  Oil  Painting .12mo,  2  00 

Eissler's  Explosives,  Nitroglycerine  and  Dynamite 8vo,  4  00 

Ford's  Boiler  Making  for  Boiler  Makers 18mo,  1  00 

Metcalfe's  Cost  of  Manufactures 8vo,  5  00 

Metcalf 's  Steel— A  Manual  for  Steel  Users 12mo,  2  00 

Reimaun's  Aniline  Colors.     (Crookes.) 8vo,  2  50 

*  Reisig's  Guide  to  Piece  Dyeing 8vo,  25  00 

Spencer's  Sugar  Manufacturer's  Handbook. . .  .12mo,  inor.  flap,  2  00 
"        Handbook      for      Chemists       of      Beet       Houses. 

12mo,  inor.  flap,  3  00 

Svedelius's  Handbook  for  Charcoal  Burners 12mo,  1  50 

The  Lathe  and  Its  Uses 8vo,  6  00 

Thurston's  Manual  of  Steam  Boilers 8vo,  5  00 

Walke's  Lectures  on  Explosives 8vo,  4  00 

West's  American  Foundry  Practice 12mo,  2  50 

"      Moulder's  Text-book 12mo,  2  50 

Wiechmauu's  Sugar  Analysis 8vo,  2  50 

Woodbury's  Fire  Protection  of  Mills 8vo,  2  50 


MATERIALS  OF  ENGINEERING. 

STRENGTH — ELASTICITY — RESISTANCE,  ETC. 
(See  also  ENGINEERING,  p.  6.) 

Baker's  Masonry  Construction 8vo,  .$5  00 

Beardslee  and  Kent's  Strength  of  Wrought  Iron 8vo,  1  50 

Bovey's  Strength  of  Materials 8vo,  7  50 

Burr's  Elasticity  and  Resistance  of  Materials Svo,  5  00 

Byrne's  Highway  Construction Svo,  5  00 

Carpenter's  Testing  Machines  and  Methods  of  Testing  Materials 

Church's  Mechanic's  of  Engineering — Solids  and  Fluids Svo,  6  00 

Du  Bois's  Stresses  in  Framed  Structures 4to,  10  00 

Hatfield's  Transverse  Strains Svo,  5  00 

Johnson's  Materials  of  Construction Svo,  6  00 

Lanza's  Applied  Mechanics 3vo,  7  50 

•  "        Strength  of  "Wooden  Columns Svo,  paper,  50 

Merrill's  Stones  for  Building  and  Decoration Svo,  5  00 

Merriman's  Mechanics  of  Materials Svo,  4  00 

Strength  of  Materials 12mo,  1  00 

Patton's  Treatise  on  Foundations Svo,  5  00 

Rockwell's  Roads  and  Pavements  in  France 12mo,  1  25 

Spalding's  Roads  and  Pavements. 12mo,  2  00 

Thurston's  Materials  of  Construction , , Svo,  5  00 

Thurston's  Materials  of  Engineering 3  vols.,  Svo,  8  00 

Vol.  I.,  Non-metallic. Svo,  200 

Vol.  II. ,  Iron  and  Steel Svo,  3  50 

Vol.  III.,  Alloys,  Brasses,  and  Bronzes Svo,  2  50 

Weyrauch's  Strength  of  Iron  and  Steel.    (Du  Bois.) Svo,  1  50 

Wood's  Resistance  of  Materials Svo,  2  00 

MATHEMATICS. 

CALCULUS—  GEOMETRY — TRIGONOMETRY,  ETC. 

Baker's  Elliptic  Functions Svo,  1  50 

Ballard's  Pyramid  Problem Svo,  1  50 

Barnard's  Pyramid  Problem Svo,  1  50 

Bass's  Differential  Calculus 12mo,  4  00 

Brigg's  Plane  Analytical  Geometry , 12mo,  1  00 

Chapman's  Theory  of  Equations 12mo,  1  50 

10 


Chessin's  Elements  of  the  Theory  of  Functions 

Compton's  Logarithmic  Computations 12nio,  $1  50 

Craig's  Linear  Differential  Equations 8vo,  5  00 

Davis' s  Introduction  to  the  Logic  of  Algebra 8vo,  1  50 

Halsted's  Elements  of  Geometry ..8vo,  1  75 

Synthetic  Geometry 8vo,  150 

Johnson's  Curve  Tracing 12mo,  1  00 

"        Differential  Equations — Ordinary  and  Partial 8vo,  3  50 

"        Integral  Calculus 12mo,  1  50 

"  "  "          Unabridged 

Least  Squares , 12mo,  150 

Ludlow's  Logarithmic  and  Other  Tables.     (Bass.) 8vo,  2  00 

Trigonometry  with  Tables.     (*Bass.) 8vo,  300 

Mahan's  Descriptive  Geometry  (Stone  Cutting) 8vo,  1  50 

Merriman  and  Woodward's  Higher  Mathematics 8vo,  5  00 

Merrimau's  Method  of  Least  Squares 8vo,  2  00 

Parker's  Quadrature  of  the  Circle 8vo,  2  50 

Rice  and  Johnson's  Differential  and  Integral  Calculus, 

2  vols.  in  1,  12mo,  2  50 

Differential  Calculus 8vo,  350 

Abridgment  of  Differential  Calculus.... 8vo,  150 

Searles's  Elements  of  Geometry 8vo,  1  50 

Totten's  Metrology 8vo,  2  50 

Warren's  Descriptive  Geometry 2  vols.,  8vo,  3  50 

' '        Drafting  Instruments 12mo,  1  25 

'<        Free-hand  Drawing 12mo,  100 

"        Higher  Linear  Perspective 8vo,  3  50 

"        Linear  Perspective 12mo,  1  00 

"        Primary  Geometry 12mo,  75 

Plane  Problems... 12mo,  125 

"        Plane  Problems 12mo,  125 

"        Problems  and  Theorems 8vo,  2  50 

Projection  Drawing 12mo,  1  50 

Wood's  Co-ordinate  Geometry 8vo,  2  00 

Trigonometry 12mo,  100 

Woolf's  Descriptive  Geometry Royal  8vo,  3  00 

11 


MECHANICS- MACHINERY. 

TEXT-BOOKS  AND  PRACTICAL  WORKS. 
(See  also  ENGINEERING,  p.  6.) 

Baldwin's  Steam  Heating  for  Buildings .' . .  .12mo,  $2  50 

Benjamin's  Wrinkles  and  Recipes 12mo,  2  00 

Carpenter's  Testing  Machines  and   Methods   of   Testing 

Materials 8vo, 

Chordal's  Letters  to  Mechanics 12mo,  2  00 

Church's  Mechanics  of  Engineering 8vc,  6  00 

"        Notes  and  Examples  in  Mechanics 8vo,  2  00 

Crehore's  Mechanics  of  the  Girder 8vo,  5  00 

Cromwell's  Belts  and  Pulleys 12mo,  1  50 

Toothed  Gearing 12mo,  150 

Compton's  First  Lessons  in  Metal  Working 12mo,  1  50 

Dana's  Elementary  Mechanics 12mo,  1  50 

Dingey's  Machinery  Pattern  Making 12mo,  2  00 

Dredge's     Trans.     Exhibits     Building,      World     Exposition, 

4to,  half  morocco,  10  00 

Du  Bois's  Mechanics.     Vol.  I.,  Kinematics 8vo,  3  50 

Vol.  II.,  Statics .8vo,  400 

Vol.  III.,  Kinetics 8vo,  3  50 

Fitzgerald's  Boston  Machinist 18mo,  1  00 

Flather's  Dynamometers 12nio,  2  00 

Rope  Driving 12mo,  200 

Hall's  Car  Lubrication 12mo,  1  00 

Holly's  Saw  Filing 18mo,  75 

Jones  Machine  Design.     Part  I,  Kinematics 8vo,  1  50 

"  "  Part  II,  Strength  and   Proportion  of 

Machine  Parts 

Lanza's  Applied  Mechanics 8vo,  7  50 

MacCord's  Kinematics .8vo,  5  00 

Merriman's  Mechanics  of  Materials .8vo,  4  00 

Metcalfe's  Cost  of  Manufactures .8vo,  5  00 

Michie's  Analytical  Mechanics 8vo,  4  00 

Mosely's  Mechanical  Engineering.     (Mahan.) • 8vo,  5  00 

Richards's  Compressed  Air 12mo,  1  50 

Robinson's  Principles  of  Mechanism 8vo,  3  00 

Smith's  Press-working  of  Metals 8vo,  8  00 

12 


The  Lathe  and  Its  Uses .  8vo,  $6  00 

Thurstou's  Friction  and  Lost  Work 8vo,  3  00 

The  Animal  as  a  Machine 12mo,  1  00 

Warren's  Machine  Construction 2  vols.,  8vo,  7  50 

Weisbach's  Hydraulics  and  Hydraulic  Motors.    (Du  Bois.)..8vo,  500 
Mechanics    of    Engineering.      Vol.    III.,    Part   I., 

Sec.  I.     (Klein.)... 8vo,  500 

Weisbach's   Mechanics    of  Engineering.     Vol.    III.,    Part   I., 

Sec.  II      (Klein.) 8vo,  500 

Weisbach's  Steam  Engines.     (Du  Bois.) 8vo,  5  00 

Wood's  Analytical  Mechanics 8vo,  3  00 

"      Elementary  Mechanics 12mo,  125 

Supplement  and  Key 1  25 

METALLURGY. 

IKON— GOLD— SILVER — ALLOYS,  ETC. 

Allen's  Tables  for  Iron  Analysis 8vo,  3  00 

Egleston's  Gold  and  Mercury 8vo,  7  50 

Metallurgy  of  Silver 8vo,  750 

*  Kerl's  Metallurgy — Copper  and  Iron 8vo,  15  00 

*  "                            Steel,  Fuel,  etc 8vo,  1500 

Kunhardt's  Ore  Dressing  in  Europe. 8vo,  1  50 

Metcalf  Steel— A  Manual  for  Steel  Users 12mo,  200 

O'Driscoll's  Treatment  of  Gold  Ores. 8vo,  2  00 

Thurston's  Iron  and  Steel 8vo,  3  50 

Alloys 8vo,  250 

Wilson's  Cyanide  Processes 12mo,  1  50 

MINERALOGY   AND  MINING. 

MINE  ACCIDENTS — VENTILATION— »ORE  .DRESSING,  ETC. 

Barriuger's  Minerals  of  Commercial  Value. . .  .oblong  morocco,  2  50 

Beard's  Ventilation  of  Mines 12mo,  2  50 

Boyd's  Resources  of  South  Western  Virginia 8vo,  3  00 

'":  "      Map  of  South  Western  Virginia Pocket-book  form,  2  00 

Brush  and  Penfield's  Determinative  Mineralogy 8vo,  3  50 

Chester's  Catalogue  of  Minerals 8vo,  1  25 

"              "           "        "         paper,  50 

Dictionary  of  the  Names  of  Minerals 8vo,  3  00 

Dana's  American  Localities  of  Minerals , 8vo,  1  00 

13 


Dana's  Descriptive  Mineralogy.     (E.  S.)  . . .  .8vo,  half  morocco,  $12  50 

Mineralogy  and  Petrography.     (J.  D.) 12mo,  200 

"      Minerals  and  How  to  Study  Them.     (E.  S.). 12mo,  1  50 

"      Text-book  of  Mineralogy.     (E.  S.) 8vo,  3  50 

^Drinker's  Tunnelling,  Explosives,  Compounds,  and  Rock  Drills. 

4to,  half  morocco,  25  00 

Egleston's  Catalogue  of  Minerals  and  Synonyms 8vo,  2  50 

Eissler's  Explosives — Nitroglycerine  and  Dynamite 8vo,  4  00 

Goodyear's  Coal  Mines  of  the  Western  Coast . 12mo,  2  50 

Hussak's  Rock  forming  Minerals.     (Smith.) Svo,  2  00 

Ihlseng's  Manual  of  Mining. . Svo,  4  00 

Kuuhardt's  Ore  Dressing  in  Europe Svo,  1  50 

O'Driscoll's  Treatment  of  Gold  Ores Svo,  2  00 

Rosenbusch's    Microscopical    Physiography   of    Minerals    and 

Rocks.     (Iddiugs.) Svo,  500 

Sawyer's  Accidents  in  Mines Svo,  7  00 

StDskbridge's  Rocks  and  Soils Svo,  2  50 

Walke's  Lectures  on  Explosives Svo,  4  00 

Williams's  Lithology Svo,  3  00 

Wilson's  Mine  Ventilation 16nio,  1  25 

STEAM  AND  ELECTRICAL  ENGINES,  BOILERS,  Etc. 

STATION  AH  Y— MARINE— LOCOMOTIVE — GAS  ENGINES,  ETC. 
(See  also  ENGINEERING,  p.  6.) 

Baldwin's  Steam  Heating  for  Buildings. 12mo,  2  50 

Clerk's  Gas  Engine , 12mo,  4  00 

Ford's  Boiler  Making  for  Boiler  Makers ISmo,  1  00 

Hemeuway's  Indicator  Practice 12mo,  2? 00 

Hoadley's  Warm-blast  Furnace Svo,  1  50 

Kneass's  Practice  and  Theory  of  the  Injector Svo,  1  50 

MacCord's  Slide  Valve Svo,  2  00 

*Maw's  Marine  Engines Folio,  half  morocco,  18  00 

Meyer's  Modern  Locomotive  Construction 4to,  10  00 

Peabody  and  Miller's  Steam  Boilers Svo,  4  00 

Peabody's  Tables  of  Saturated  Steam Svo,  1  00 

Thermodynamics  of  the  Steam  Engine Svo,  5  00 

Valve  Gears  for  the  Steam  Engine Svo,  2  50 

Pray's  Twenty  Years  with  the  Indicator Royal  Svo,  2  50 

Pupin  and  Osterberg's  Thermodynamics 12nio,  1  25 

Reagan's  Steam  and  Electrical  Locomotives 12mo,  2  00 

Routgen's  Thermodynamics.     (Du  Bois.) Svo,  5  00 

Sinclair's  Locomotive  Running 12mo,  2  00 

Thurston's  Boiler  Explosion 12mo,  1  50 

14 


Thurstoii's  Eugine  and  Boiler  Trials 8vo,  $5  00 

Manual  of  the  Steam  Engine.      Part  I.,  Structure 

and  Theory, 8vo,  7  50 

Manual  of  the    Steam  Engine.      Part  II.,    Design, 

Construction,  and  Operation 8vo,  7  50 

2  parts,  12  00 

Philosophy  of  the  Steam  Engine 12ino,  75 

Reflection  on  the  Motive  Power  of  Heat.    (Caruot.) 

12mo,  1  50 

"           Stationary  Steam  Engines 12mo..  1  50 

Steam-boiler  Construction  and  Operation 8vo,  5  00 

Spaugler's  Valve  Gears 8vo,  2  50 

Trowbridge's  Stationary  Steam  Engines 4to,  boards,  2  50 

Weisbach's  Steam  Engine.     (Du  Bois.) 8vo,  5  00 

Whitham's  Constructive  Steam  Engineering 8vo,  10  00 

Steam-engine  Design 8vo,  6  00 

Wilson's  Steam  Boilers.     (Flather.) 12mo,  2  50 

Wood's  Thermodynamics,  Heat  Motors,  etc 8vo,  4  00 

TABLES,  WEIGHTS,  AND  MEASURES. 

FOR  ACTUARIES,  CHEMISTS,  ENGINEERS,  MECHANICS— METRIC 
TABLES,  ETC. 

Adriauce's  Laboratory  Calculations 12rno,  1  25 

Allen's  Tables  for  Iron  Analysis., 8vo,  3  00 

Bixby's  Graphical  Computing  Tables Sheet,  25 

Comptou's  Logarithms 12mo,  1  50 

Craudall's  Railway  and  Earthwork  Tables 8vo,  1  50 

Egleston's  Weights  and  Measures 18mo,  75 

Fisher's  Table  of  Cubic  Yards Cardboard,  25 

Hudson's  Excavation  Tables.     Vol.  II 8vo,  1  00 

Johnson's  Stadia  and  Earthwork  Tables 8vo,  1  25 

Ludlow's  Logarithmic  and  Other  Tables.     (Bass.) 12mo,  2  00 

Thurstoii's  Conversion  Tables Svo,  1  00 

Totteu's  Metrology Svo,  2  50 

VENTILATION. 

STEAM  HEATING — HOUSE  INSPECTION — MINE  VENTILATION. 

Baldwin's  Steam  Heating 12mo,  2  50 

Beard's  Ventilation  of  Mines 12mo,  2  50 

Carpenter's  Heating  and  Ventilating  of  Buildings. Svo,  3  00 

Gerhard's  Sanitary  House  Inspection Square  16ino,  1  00 

Mott's  The  Air  We  Breathe,  and  Ventilation 16mo,  1  00 

Reid's  Ventilation  of  American  Dwellings 12mo,  1  50 

Wilson's  Mine  Ventilation 16mo,  1  25 

15 


niSQELLANEOUS   PUBLICATIONS. 

Alcott's  Gems,  Sentiment,  Language Gilt  edges,  $5  00 

Bailey's  The  New  Tale  of  a  Tub 8vo,  75 

Ballard's  Solution  of  the  Pyramid  Problem 8vo,  1  50 

Barnard's  The  Metrological  System  of  the  Great  Pyramid.  .8vo,  1  50 

Davis'  Elements  of  Law 8vo,  2  00 

Emmon's  Geological  Guide-book  of  the  Rocky  Mountains.  .8vo,  1  50 

Ferrel's  Treatise  "on  the  Winds 8vo,  4  00 

Haines'  Addresses  Delivered  before  the  Am.  Ry.  Assn. . .  .12mo.  2  50 

Mott's  The  Fallacy  of  the  Present  Theory  of  Sound . .  Sq.  16mo,  1  00 

Perkins's  Cornell  University Oblong  4to,  1  50 

Ricketts's  History  of  Rensselaer  Polytechnic  Institute. . .  .  8vo,  3  00 
Rctherham's    The    New    Testament     Critically    Emphasized. 

12m  o,  1  50 
"              The  Emphasized  New  Test.     A  new  translation. 

large  8vo,  2  00 

Totteu's  An  Important  Question  in  Metrology. 8vo,  2  50 

Whitehouse's  Lake  Mceris „ Paper,  25 

*  Wiley's  Yosemite,  Alaska,  and  Yellowstone 4to,  3  00 

HEBREW  AND  CHALDEE  TEXT=BOOKS. 

FOR  SCHOOLS  AND  THEOLOGICAL  SEMINARIES. 

Gesenius's  Hebrew  and   Chaldee  Lexicon  to  Old   Testament. 

(Tregelles.). Small  4to,  half  morocco,  5  00 

Green's  Elementary  Hebrew  Grammar. 12mo,  1  25 

"       Grammar  of  the  Hebrew  Language  (New  Edition). 8 vo,  3  00 

"       Hebrew  Chrestomathy. 8vo,  2  00 

Letteris's    Hebrew  Bible  (Massoretic  Notes  in  English). 

8vo,  arabesque,  2  25 
Luzzato's  Grammar  of  the  Biblical  Chaldaic  Language  and  the 

Talmud  Babli  Idioms 12mo,  1  50 

MEDICAL. 

Bull's  Maternal  Management  in  Health  and  Disease 12mo,  1  00 

Hammarsteu's  Physiological  Chemistry.    (Mandel.) 8vo,  4  00 

Mott's  Composition,  Digestibility,  and  Nutritive  Value  of  Food. 

Large  mounted  chart,  1  25 

Ruddiman's  Incompatibilities  in  Prescriptions. 8vo,  2  00 

Steel's  Treatise  on  the  Diseases  of  the  Ox. ...   8vo,  6  00 

"      Treatise  on  the  Diseases  of  the  Dog 8vo,  3  50 

Worcester's  Small  Hospitals— Establishment  and  Maintenance, 
including  Atkinson's  Suggestions  for  Hospital  Archi- 
tecture   i  i  ia™/»  1  25 

16 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


OCT  28  1916 


AY  SI  >r' 


8 

HA..  4   1920 
DEC    1    1988 


/If/jy 


APR  2 7  1966     Q 

-61-85 


30m-l,'15 


